although the invention will be described in terms of a specific embodiment , it will be readily apparent to those skilled in this art that various modifications , rearrangements and substitutions can be made without departing from the spirit of the invention . the scope of the invention is defined by the claims appended hereto . referring in general to fig1 - 3 , set forth is a side elevational view of the adjustable child seat for bicycles 10 of the instant invention . the child seat 10 is coupled to a bicycle frame 100 having a handlebar support post 102 which secures handlebars 104 in a fixed position . the bicycle frame 100 typically includes an upper railing 106 , lower railing 108 , and front wheel support 110 . front wheel support 110 provides the support structure for the rotating wheel 112 , all of which is used in steering the bicycle upon the rotation of handlebars 104 , commonly held along the handgrip 114 . the seat 10 is formed from a main frame support 12 having a forward upper support 14 forming a u - shaped structure securable to rear upper support 16 . the first end 18 and second end 20 of the rear upper support 16 accepts the insertion ends 70 , 72 of the forward upper support 14 in a nested arrangement . more specifically , the first and second ends 18 , 20 of the rear upper support 16 act as tubular receptacles into which the insertion ends 70 , 72 are slid and secured . the movement allows for adjustment and securement by use of carriage bolts 22 and 24 which may be placed into through holes 26 . the spacial separation of the forward upper support 14 and rearward upper support 16 provides for an enlarged opening , further described later in this description , wherein placement of the carriage bolts 22 and 24 in one of the through holes which allows for the support of a child of approximately nine months . by movement of the carriage bolts 22 and 24 into the furthermost through hole , an enlarged opening is formed which is receptive to a child of approximately four years old . the main frame support 12 includes a handlebar support clamp 32 which allows securement of the main frame to the handlebar 104 . as will be described later in the specification , spacers 80 can be added or removed , as needed . the spacers 80 work in conjunction with a carriage bolt 34 to allow for proper vertical positioning of the main frame in relation to the steering support post 102 . a wing nut 36 is attached to the end of the carriage bolt 34 and allows for ease of attachment of the main frame to the handlebars without tools . the main frame 12 includes a left vertical support 28 and right vertical support 30 . left leg extension 38 couples to the left leg vertical support 28 by use of a carriage bolt 40 with wing nut 42 to allow for the placement of the left leg extension 38 along the vertical length of the left . vertical support . similarly , the right vertical support 30 includes a right leg extension 46 having carriage bolt 48 and wing nut 50 for use in supporting the right leg extension 46 along the vertical length of the right vertical support 30 . each leg extension includes a raised tab to inhibit the outward movement of a child &# 39 ; s foot . the tab further assists in maintaining the seat in a formed position . the seat 52 is formed from a single piece of material having a plurality of apertures formed by the overlapping of the material for use in securing the seat to the frame , without the use of tools . the seat apertures are formed from overlapped material 54 that is secured in position by thread or the like permanent attachment means . a first seat aperture is formed along the rear section 56 of the rear upper support 16 . the first seat aperture is receptive to the rear upper support member providing a backing support to the seat structure . the seat structure is further formed from an aperture placed over the forward upper support 14 along section 58 between the two handlebar mounts 30 . in addition , leg portions 60 and 62 of the seat 52 include securement portions 64 and 66 which each encompass the lower leg extensions . the material providing a comfortable placement for the legs of the child while operating to prevent movement of the leg in a position that would allow contact with the rotating wheel 112 . now referring in general to fig4 - 6 , the main frame support structure 12 is further illustrated and defined as a forward upper support section 14 having a lower support portion being bifurcated as depicted by numerals 28 and 30 . the lower support portions are positionable on each side of the steering post . the forward upper support portion 14 is operatively associated with the rearward upper support portion 16 which has a first end 18 and a second end 20 forming an outer tubular structure receptive to the insertion ends 70 and 72 of the forward support structure which each form an inner tubular structure slidably insertable into the rearward structure . through hole 74 is alignable with one of the through holes 26 wherein placement of a carriage bolt into the through holes adjustably secures the rear upper support to the forward upper support . depending upon the alignment of the through holes , the forward and rearward upper supports can be spacially positioned to allow for the securement of various sized children . fig4 a and 4b depict the first attachment means described as the handlebar attachment for securing the forward upper support to the handlebars of the steering mechanism . the attachment means consists of a first clamp 76 which is spaced apart from a second clamp 78 by a series of spacers 80 . the spacers may be of any size allowing removal of one or more spacers to allow for the customization of the mount to a particular handlebar configuration . carriage bolt 82 includes a wing nut 84 that secures the clamps 76 and 78 in a spaced - apart secure arrangement . in this manner , clamp 76 is placed over the forward upper support and clamp 78 is placed over the handle bar . upon attachment of carriage bolt 82 , the wing nut 84 securely fastens the forward upper support to the handle bars . during installation , or movement from one bicycle to another , a spacer 80 may be removed wherein the spatial distance between clamp 76 and 78 is decreased . the spacer may be saved for later use if another installation requires an additional space between the clamp so as to place the frame in a substantially vertical position . as shown in fig4 b , which is an alternative side view of 4a , the clamp 76 and 78 form a mirror image allowing for interchangeability . fig5 further illustrates the main frame support 12 to include a handlebar bracket 86 , also shown in fig4 which maintains the bifurcated lower support members in a spaced - apart position and allows for coupling of the main frame to the steering post . the handlebar bracket support 88 may be fastened to the handlebar bracket 86 by the use of a carriage bolts 91 and 91 thereby securing the lower portion of the main frame to the steering post . the handlebar clamp 32 and the handlebar bracket 86 provide a three point coupling stance for superior stability . the leg extension support 38 descends from the lower support portion of the main frame and includes a tubular shaped upper portion 90 which is slidably insertable into the distal end 92 of the bifurcated structure . through hole 94 is available for alignment with one of the through holes 96 of the leg extension , thereby allowing for a full adjustment of the leg extension in relation to the main frame to accommodate the various size legs of the child placed within the seat . as previously mentioned , a carriage bolt may be placed into the through hole for securement of the leg extension in a predetermined position . now referring to fig7 set forth is a seat 52 which is formed of a single piece of material having a rearward aperture 56 formed by taking a portion of the seat material and forming the aperture by sewing the fabric together providing a continuous loop for placement of the rearward upper support . similarly , leg portion 60 includes an attachment area 64 as well as leg portion 62 having attachment area 66 . center portion 58 includes an attachment portion for securement of the seat to the front upper support . extension 60 includes a side support 97 which secures to the leg extension and placed at such a position so as to encompass the mounting bolts to prevent scratching of the child as well as leg extension 62 having attachment 98 providing duplicate function . as shown in fig8 the seat 52 forms a cup shape so as to protect the child from sliding backwards or forwards with leg portion 62 extending downward for support of the leg in prevention of the leg from engaging the wheel . the bicycle seat is modular in construction allowing for compact shipping and ease of assembly . the seat material is light weight and easily washed , if soiled , or replaced if necessary . it is to be understood that while a certain form of the invention is illustrated , it is not to be limited to the specific form or arrangement of parts herein described and shown . it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification .