reference will now be made in detail to the preferred embodiments of the invention , examples of which are illustrated in the accompanying drawings . while the invention will be described in conjunction with the preferred embodiments , it will be understood that they are not intended to limit the invention to those embodiments . on the contrary , the invention is intended to cover alternatives , modifications and equivalents , which may be included within the spirit and scope of the invention as defined by the appended claims . as shown in fig1 - 7 , neck 11 is formed on a thin - walled jar or other container and has a curved primary seal surface 12 which is very smooth and is distinguished by the absence of parting lines or parting line defects inasmuch as it is formed by air pressure or other mechanical means during the blow molding process . primary seal surface 12 is not formed by the mold halves and thus does not have a mold parting line or associated parting line defects formed therein . as shown in fig2 the seal surface 12 can be curved . further , the primary sealing surface has minimal ovality , by reason of the way it is formed . above surface 12 the neck structure extends outwardly in a outward stretch 13 which terminates in an upward bend 14 . above bend 14 is a thin , tapered upward - inward extending flange 16 , the inner edge of which is of greater diameter than the diameter of surface 12 . below surface 12 the neck extends downwardly - outwardly in a slanted stretch 17 which terminates in a short vertical stretch 18 , there being an inward directed substantially horizontal upper shoulder 19 below surface 18 . vertical stretch 21 extends downwardly from the inner edge of shoulder 19 terminating in an inwardly curved portion 22 which merges with an outward - downward stretch 23 . an approximately vertical short surface 24 , which has a greater diameter than surface 18 , terminates in a second or lower horizontal inward directed shoulder 26 . vertical stretch 27 depends from the inner edge of shoulder 26 , merging with an outward bend 28 which merges with an outward - downward stretch 29 . the lower end of stretch 29 merges with a downward stretch 30 which , in turn , merges an inward - downward stretch 31 . in accordance with one form of standard blow molding practice , a parison of plastic material from which the container is to be formed is deposited in the split mold . it will be understood that the type plastic used to mold the container and the neck may be any suitable relatively hard plastic such as polyethylene . air is blown into the parison to expand it to fill the mold . in one form of the present invention , the mold has an insert which shapes the finish of the neck of the container heretofore described and above the neck insert the mold widens out to establish what is known as a blow dome of excess material . in accordance with one form of the present invention , as distinguished from prior neck finishes , the blow mold is severed at the inner edge of flange 16 , as by trimming . severing the edge of the neck from the blow dome may cause a rough surface . one of the advantages of the present invention is that the edge of flange 16 at which the blow dome is severed is not the primary sealing surface . instead , primary seal surface 12 is located below and removed from the trimmed edge of flange 16 . the blow dome may be severed or sheared from the neck by such methods as trimming to diameter , or by other methods including a subsequent shearing operation on a separate machine or including the use of shear inserts on the molding apparatus . other well - known means may shear the blow dome from the neck finish so long as the shear edge is not the primary sealing surface . likewise , other means may be used for terminating the inner edge of flange because that the inner edge does not engage the cap used therewith in a sealing fashion . directing attention to fig2 a blow dome 33 has an outward - upward slanted stretch 34 merging into a curved stretch 36 which has an inward slanted stretch 37 . the cut line 38 is a circle wherein the stretch 34 is severed from the inner edge of flange 16 . preferably flange 16 should terminate so that it does not engage the plug of the cap in a sealing fashion . by reason of the almost 180 ° bend 14 , and the rapid diameter changes within a relatively short vertical distance , flange 16 is thin and flexible . one form of closure or cap 41 used with the present invention is shown in fig3 - 7 . the closure of fig3 - 7 comprises an indented circular top 42 having a short peripheral cylindrical upward extending member 43 from which extends outwardly a stack rim 44 . the outer edge of rim 44 has a depending downward stretch 46 which merges into a vertical , substantially cylindrical upper outer skirt 48 . the lower end of upper outer skirt 48 merges into an outward - downward slanted stretch 55 . below stretch 55 is a substantially cylindrical lower outer skirt 49 . an internal score line or line of weakness 51 separates stretch 55 from lower skirt 49 . below lower skirt 49 , cap 41 has an outward - downward slanted flange 52 which , for practical purposes , rests against outward - downward surface 29 of neck 11 . interrupted upper inner bead sections 53 engage under shoulder 19 of neck 11 . lower inner bead 54 located at the lower end of skirt portion 49 engages under shoulder 26 of neck 11 . when cap 41 is attached to neck 11 , beads 53 and 54 prevent cap 41 from being removed from neck 11 . in order to enable the user to grip cap 41 , ribs 50 extend outwardly from upper outer skirt member 48 merging with the outer surface of lower skirt portion 49 as best shown in fig7 . ribs 50 also impart columnar strength to the closure to transfer vertical force and prevent closure collapse during axial application of the closure to the neck finish . at one portion of the circumference of lower skirt 49 , as best shown in fig5 and 6 , spaced outwardly therefrom is a horizontal pull tab 57 having a curved connection 58 to lower skirt 49 . the interior of skirt 49 is formed with a notch 59 where tab 57 joins lower skirt 49 . notch 59 forms a vertical line of weakness through lower skirt 49 . enlargement 61 is formed on the distal edge of pull tab 57 . a portion of flange 52 is formed thinner than the rest of flange 52 in a thin area 62 adjacent tab 57 . cap 41 includes a downward extension of cylindrical member 43 which forms a depending inner skirt extension 66 . the lower inner edge of depending inner skirt extension 66 is formed with a radius 67 . the inner surface of cylindrical member 43 seals against primary seal surface 12 . a vertical position of cap top 42 can be adjusted to provide for compression of surface 12 against the adjacent surface of member 43 . directing attention to fig7 it will be seen that the surface 12 is the primary sealing surface against the member 43 . as has been noted , the surface 12 is very smooth and hence forms a very effective seal against the member 43 . when the cap is applied , beads 53 and 54 lock under shoulders 19 and 26 to prevent removal of cap 41 from neck 11 and hence are tamper evidencing . when the user wishes to open the container , the user grips the enlargement 61 and bends pull tab 57 outwardly and then pulls circumferentially , tearing lower skirt 49 from upper cap portion , namely , from upper skirt 48 . the user may then grip under surface 55 which , as shown in fig7 is spaced from the bottle neck finish by a considerable gap , and pull upwardly causing the interrupted upper bead segments 53 to disengage from shoulder 19 so that cap 41 may be removed from neck 11 . the ribs 50 rigidify the upper portion of the cap to allow the forces necessary to push the cap onto the bottle from causing the cap to buckle . the portion of the cap above score line 51 constitutes a reclosure cap 41 and may be pressed back on neck 11 after portions of the contents of the jar or container are dispensed as frequently as required . comparison of fig7 with prior art structure shown in fig8 shows that in the present invention the very smooth surface of primary seal surface 12 causes a tight seal against the exterior of member 43 and flange 16 need not seal at all , whereas in the prior art the cut inner edge of flange 16 a is a primary seal . the primary seal surface 12 of the present invention has minimum deviation from ovality as compared to fig8 where the prior primary seal 12 a is coincident with a trim surface of flange 16 a . bottles of the type of this invention and the prior art were molded . the ovality of the two types was measured . the unexpected result of these experiments was that the current invention produced a significantly more circular primary seal area 12 . refer to table a for tabulated results . the stretch occurring on both sides of the primary seal 12 is primarily contributing to the superior ovality and differentiate it from the prior art . table a std bottle style present invention run a run b run c run d run a run b run c run d 0 . 055 0 . 020 0 . 048 0 . 028 0 . 024 0 . 058 0 . 002 0 . 015 0 . 053 0 . 002 0 . 056 0 . 015 0 . 006 0 . 010 0 . 106 0 . 030 0 . 062 0 . 000 0 . 044 0 . 010 0 . 017 0 . 002 0 . 013 0 . 010 0 . 043 0 . 010 0 . 058 0 . 003 0 . 016 0 . 004 0 . 005 0 . 027 0 . 058 0 . 029 0 . 025 0 . 009 0 . 014 0 . 013 0 . 005 0 . 034 0 . 064 0 . 016 0 . 055 0 . 003 0 . 011 0 . 060 0 . 017 0 . 017 0 . 011 0 . 005 0 . 059 0 . 002 0 . 004 0 . 003 0 . 017 0 . 019 0 . 013 0 . 049 0 . 005 0 . 007 0 . 042 0 . 006 0 . 045 0 . 002 0 . 013 average 0 . 028 average 0 . 016 [ 0058 ] fig9 illustrates a modified shape of a neck 11 b wherein seal surface 12 b is cylindrical rather than curved . as shown in fig9 the seal surface can be vertical , such as seal surface 12 b , or it may be curved , such as seal surface 12 shown in fig2 . directing attention to fig1 - 12 , various other modifications may also be made to the neck and cap of the present invention . for example , fig1 discloses an embodiment in which the primary sealing surface is disposed non - vertically and is instead an angled surface , such as seal surface 12 c shown in fig1 . upwardly extending member 43 c of cap 41 c includes a lower frustoconical portion 45 which depends from top 42 c at an angle . neck 11 c includes a non - vertical , very smooth sealing surface 12 c , an outward bend joining said sealing surface 12 c to an outward stretch 13 c , an upward bend 14 c joining outward stretch 13 b to a flange 16 c . surface 12 c is the primary sealing surface against lower portion 45 of member 43 c . the very smooth surface of primary seal surface 12 c causes a tight seal against the exterior of member 43 c whereby flange 16 c , which is joined to outward extending stretch 13 c , need not seal at all . the embodiment shown in fig1 includes a further modification in which a lower portion of lower skirt 49 c frictionally engages vertical stretch 27 c thus obviating need for an inner bead . an internal score line 51 c separates lower skirt 49 c from upper skirt 48 c . [ 0060 ] fig1 discloses an alternative embodiment of the neck and the cap . neck 11 d includes a very smooth sealing surface 12 d , an outward directed stretch 13 d joining sealing surface 12 d to an upward directed stretch 130 , and an inward directed stretch 131 joined to upward stretch 130 . inward stretch 131 terminates in an edge 132 which has a diameter greater than the diameter of seal surface 12 d and of member 43 d . the very smooth surface 12 d causes a tight seal against the exterior of member 43 d whereby edge 132 need not seal at all . the embodiment shown in fig1 includes a further modification in which cap 41 d includes a skirt 48 d having an upper inner bead 53 d , and a lower skirt 49 d having a lower inner bead 54 d . an internal score line 51 d may separate lower skirt 49 d from upper skirt 48 d . [ 0061 ] fig1 discloses an alternative embodiment of the cap without an outer skirt which may be used with the various neck embodiments discussed above . cap 41 e includes a top 42 e having a cylindrical downwardly extending member 43 e and an outwardly extending stack rim 44 e . similar to the above embodiments , seal surface 12 e causes a tight seal against the exterior of member 43 e . cap 41 e differs in that outwardly extending rim 44 e terminates in an outer edge 47 whereby cap 41 has no skirt . as noted above , such an outer skirt is not a necessary feature of the present invention because the primary sealing action takes place between the outer surface of the central plug and the sealing surface of the neck , i . e ., between member 43 e and seal surface 12 e . in the absence of a skirt , other types of tamper - evidencing methods may be employed , for example , shrink - wrapping ( not shown ). furthermore , in the absence of a skirt , other methods may also be employed to shield the upper external portion of the neck from debris and contamination . shrink - wrapping , for example , may again be employed to shield portions of the neck that are otherwise covered by a skirt from dirt . with reference to fig1 - 15 , if the contents of the container are non - viscous ( e . g ., brine - packed pickles ) or if the walls of the container are easily squeezed during transportation or handling , top 42 f may be subjected to upward pressure , as indicated by arrow “ p ” in fig1 , causing it to become “ domed ” ( outwardly convex ). such action may cause inner skirt member 43 f to pivot away from curved primary seal 12 f , resulting in leakage . this effect is illustrated in fig1 . [ 0063 ] fig1 shows one remedy for such leakage . contrasting fig1 with fig7 it will be seen that top 42 g is raised relative to stack rim 44 g and that the contact of surface 12 g with inner skirt member 43 g is more closely opposite top 42 g . fig1 also shows a structure in which top 42 g is closer to the level of rim 44 g than in the above embodiments . surface 12 g engages the surface of cylinder 43 g below the level of top 42 g . in addition , reducing the vertical spacing between top 42 g and stack rim 44 g reduces the lever arm and corresponding mechanical advantage of the inward force component generated by internal pressure . hence doming of top 42 g does not result in pivoting of skirt 66 g out of sealing contact with surface 12 g . as noted above , fig1 shows how pressure applied to the container ( as by squeezing the side wall ) may cause top 42 f to bow upward , pulling plug 66 f away from such surface 12 f . [ 0064 ] fig1 shows another remedy for leakage due to doming of surface 42 h . a plurality of angularly spaced , substantially radially gussets 71 are formed at the intersection of top 42 h and cylindrical member 43 h . gussets 71 prevent member 43 h from pivoting away from surface 12 h . a similar result can be achieved by replacing gussets 71 with a continuous reinforcing bead or shoulder at the intersection of the exterior surfaces of top 42 h and member 43 h . as shown in fig1 and 17 , another way to achieve the neck structure of the present invention is to employ what is commonly referred to as “ pull - up ” trim . in this case , the cut line is sheared by having a close diametrical fitting of a blow pin positioned internally within the parison and sets of shear steels mounted on the split mold . diameters of the blow pin are typically 0 . 001 inch to 0 . 004 inch smaller than that diameter defined by the shear steels in closed position . after blowing of the neck and the container , a portion 34 i of the parison above the cut line is severed from the neck portion below the cut line by upward movement of the blow pin relative to the shear steels as shown in fig1 . the modification shown in fig1 and 17 illustrates the formation of a modified container neck 11 i . such a neck may resemble that shown in fig1 and 2 of u . s . pat . no . 4 , 699 , 287 , (“ the &# 39 ; 287 patent ”) with an important modification , as hereinafter explained . in fig1 , the parison forming neck 11 i is shown between a blow pin 86 and shear steel 76 and neck insert 81 as molding is being completed . with continued reference to fig1 , shear steel 76 has an inward projection 77 terminating in a vertical inward extending shearing edge 78 . blow pin 86 has a lower cylindrical portion 87 having an outward extending shearing edge 88 with a groove 89 thereabove . as shown in fig1 , blow molding of the parison to the shape of shear steel 76 and neck insert 81 has just been completed . the shape of the parison generally resembles the neck shown in the &# 39 ; 287 patent . edge 88 is located below edge 78 . air blowing through hole 91 has formed vertical stretch 101 of flange 100 and inward horizontal stretch 102 as well as the portions thereabove . the smooth , vertical , lower cylindrical portion 87 has formed internal primary seal surface 12 i . the blow pin 86 then moves from the position of fig1 to the position of fig1 . the neck structure is sheared between edges 78 and 88 . inner flange edge 96 of neck 11 i is formed where the edges 78 , 88 have sheared the same and the parison sheared - off portion 94 thereabove is discarded . it is noted that edge 96 is of a larger diameter than primary seal surface 12 i . hence , a hollow plug or inner skirt such as that shown in the &# 39 ; 287 patent seated on container neck 11 i seals against surface 12 i instead of surface 96 . since blow pin 86 has no parting line , surface 12 i has no flash , that is , a parting line or parting line defects . surface 12 i is smooth and its diameter is always the same during repetitive molds and hence makes a superior seal with the cap plug . directing attention to fig1 - 20 , shear steel 76 j has an inward directed cutting edge 103 , the inside diameter of which is approximately equal to the enlarged diameter of the upper portion 104 of blow pin 86 j . below cutting edge 103 is an undercut 105 . neck insert 81 j has a seal forming projection 106 which has an inside diameter which is greater than the outside diameter of cylindrical portion 87 j of blow pin 86 j by a distance slightly less than the thickness of parison 93 j . when the neck molds are closed , the cutting edge 103 cuts off upper portion 94 j of the parison by reason of edge 103 engaging enlarged outside diameter portion 104 of blow pin 86 j . seal forming projection 106 squeezes the parison against blow pin lower portion 87 j to form a smooth , compressed primary seal surface 12 j . as shown in fig2 , when air is blown through the pin 86 j , the parison assumes the shape of neck insert 81 j . thus , neck 11 j has a primary seal surface 12 j , an outward stretch 13 j , a bend 14 j , and a cut line 38 j . the inside diameter of cut line 38 j is slightly greater than the primary seal surface 12 j . in other respects the shape of the neck 11 j resembles that of fig1 . directing attention to fig2 and 22 , neck finish 11 k and the portion above the neck finish formed in blow dome 33 k resembles that of fig2 except that screw threads 127 are formed on the exterior of upper neck surface 126 . below threads 127 , the neck has an outward curved portion 28 k which merges with horizontal shoulder 129 against which shoulder 141 on the bottom edge of cap lower skirt 49 k rests . depending from shoulder 129 k are lower ratchet teeth 128 and below teeth 128 is a remainder 146 of neck 11 k . vertical stretch 137 of cap 11 k is formed with internal threads 138 which mesh with threads 127 . on the exterior of upper cap skirt 48 k are vertical ribs 50 k and on the lower end of stretch 137 is outward directed shoulder 141 from which depend ratchet teeth 147 which mesh with ratchet teeth 128 . lower skirt 49 k is joined to shoulder 141 at juncture 148 . juncture 148 is frangible so that lower skirt 49 k and internal ratchet teeth 147 thereof may be removed to permit the cap to be unscrewed from the neck . fracture of juncture 148 indicates tampering with the contents of the container . below lower skirt 49 k is a downward - outward directed flange 149 which is in close proximity to remainder 146 of the neck so as to prevent foreign matter from entering between the ratchet teeth . [ 0075 ] fig2 and 24 illustrate a modified neck finish 11 l similar to that shown above and having external screw threads 127 l formed on the neck structure to replace the snap - on structure described above with reference to fig1 . fig2 is an enlarged view of a portion of fig2 showing the positioning of ratchet teeth 128 l which are interengaged by internal ratchet teeth on the lower portion of a cap skirt similar to that shown in fig2 . directing attention now to fig2 , a different shape neck is produced by the mold parts therein illustrated . blow pin 86 m has a lower tapered portion 111 at the upper end of which is a vertical cylindrical surface 115 which is smooth and terminates at its upper end in a shear corner 114 . above corner 114 is a cut - away 116 . blow pin 86 m may be made of two parts in order to facilitate fabrication . as shown in fig2 , lower portion 86 m is attached to upper blow pin portion 113 and radial grooves or channels 112 are cut in the top surface of blow pin 86 m , the channels 112 being connected to vertical air holes 91 m . thus when air is blown into blow pin 86 m air travels up holes 91 g and out channels 112 . the lower corner of upper blow pin 113 is formed with a cut - away 117 which merges with cut - away 116 to clear inward shearing edge 78 m of inward extension 77 m of shear steel 76 m . the upper end of neck insert 81 m is formed with seal forming projection 106 m which presses the parison against surface 115 . the neck formed in neck insert 81 m has external threads and hence grooves 118 for such threads are formed therein . below the threaded portion of the neck , the bottle may assume any desired shape and hence the details of neck insert 81 m which form the same are not specifically set forth . after the neck has been blown , as shown in fig2 , the blow pin 86 m is raised and hence the shear corner 114 shears off the parison by shearing action against edge 78 m . thus the neck has a straight upward section 122 which is a smooth sealing surface characterized by the absence of mold parting lines and also characterized by the absence of rough edges . directing attention to fig2 , the neck 11 m formed in the mold parts shown in fig2 is illustrated with a cap 41 m snapped thereon . thus neck 11 m has an upper lip 121 below which is a vertical , smooth , seamless seal surface 122 with an enlarged diameter portion 123 m therebelow . on the outside of the neck 11 m there is an upper , vertical , straight surface 126 m below which are external threads 127 m . below the threads is an outward curved portion 28 m which merges with an horizontal shoulder 129 m . below the shoulder 129 m are outward extending vertical ratchet teeth 128 m , and below the teeth 128 m is remainder 146 m of the neck . cap 41 m has a top 42 m with a vertical outer skirt 48 m depending from the outer edge thereof . upper skirt 48 m is connected to lower skirt 49 n as hereinafter appears . the upper edge of skirt 48 m is connected to top 42 m by corner 136 , and below corner 136 is a substantially vertical stretch 137 m , the inner surface of which is formed with internal threads 138 m which mate with external threads 127 m of neck 11 m . on the exterior of upper skirt 48 m are vertical ribs 59 m which assist the user in unscrewing the cap . an inner filet 140 is formed at the juncture of the underside of top 42 m and the inside of upper skirt 48 m . the purpose of fillet 141 is to exert pressure against the upper portion of the neck 11 m to force seal surface 122 m outwardly . the inner surface of lower skirt 49 m is formed with ratchet teeth 147 m which mate with teeth 128 m . the upper inner corners of teeth 128 m are joined to shoulder 141 m on the lower end of upper skirt 48 m at frangible juncture points 148 m . below lower skirt 49 m is an outward , downward slanted flange 149 m which engages the outside of skirt portion 29 m . depending from top 42 m is a plug or inner skirt 66 m having a radius 67 m at its lower , outer corner . when the neck 11 m is forced outwardly by fillet 140 , it tightly engages the outside surface of plug 66 m to form a liquid tight seal . it will be seen that the cap shown in fig2 is tamper - evidencing . when the cap 41 m is unscrewed , the junctures 148 m fracture , permitting the cap to be unscrewed but so long as the junctures 148 m are intact , evidence that the cap has not been opened appears . directing attention to fig2 - 28 , a neck similar to that of fig2 is produced . the molding process used is generally known as “ ram down ” molding in that the blow pin 86 n is forced down on striker plate 156 . blow pin 86 n has an upper cylindrical portion 104 n , a reduced diameter portion 87 n below portion 104 n , and a curved portion 157 intermediate portions 87 n and 104 n . a corner 88 n at the juncture of curved portion 157 and upper portion 104 n comprises a cutting edge . neck insert 81 n resembles that of fig2 . above neck insert 81 n is a striker plate 156 having a rounded point 158 which is opposite curved portion 157 when blow pin 86 n is in down position , as shown in fig2 . the spacing between point 158 and curved portion 157 is slightly less than the thickness of parison 93 n . as shown in fig2 , when pin 81 n is in down position , cutting edge 88 n engages striker plate point 158 thereby shearing off parison portion 94 n . the parison 93 n is squeezed between point 158 and curved portion 157 , thereby creating primary seal surface 12 n . [ 0083 ] fig2 shows the neck structure 11 p of fig2 with a cap 41 p seated thereon . thus it will be seen that the outward stretch 13 p of neck 11 p does not engage either the underside of cap top 42 p nor the plug 66 p nor the upper skirt 48 p . it will be understood that different neck shapes are shown formed by the various types of molds and molding methods illustrated in the drawings and described herein . however the neck shapes and molding techniques may be interchangeable , as will occur to one skilled in the art . in fig8 - 28 the same reference numerals are used for parts corresponding to those elsewhere mentioned , followed by subscripts a , b , c , d , e , f g , h , i , j , k , l , m , n and p , respectively . the foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description . they are not intended to be exhaustive or to limit the invention to the precise forms disclosed , and obviously many modifications and variations are possible in light of the above teaching . the embodiments were chosen and described in order to best explain the principles of the invention and its practical application , to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated . it is intended that the scope of the invention be defined by the claims appended hereto and their equivalents .