a compression cap in accordance with the preferred embodiment is shown in fig3 and generally designated 10 . the cap 10 is preferably a metal band that is capable of slidably fitting over a pipe or tube 12 . the cap 10 preferably includes a plurality of spaced apart ribs 14 , a positive stop flange 16 , and a witness window 18 . in operation , the cap 10 is placed over the end of a pipe 12 , and a fitting 22 is inserted into the cap 10 at the same end of the pipe 12 . the cap 10 is then crimped with a crimping tool ( not shown ) to compress the cap 10 about the pipe 12 and the fitting 22 , securing the fitting 22 inside the pipe 12 . shown in fig6 and 7 , the pipe 12 is well known and generally comprised of , but not limited to , plastic , such as pvc or pex ( cross linked polyethylene ). the pipe includes an outer surface 19 , and an end 23 that will receive the cap 10 . depending on the desired application , the pipe may be a rigid or flexible , and may have a variety of standard sizes . the fitting 22 is also well known and is available in standard sizes . they are generally comprised of a metal , such as brass , or plastic , and include at least one insert 21 having a diameter slightly smaller than the inner diameter of the pipe 12 such that it can be inserted into the end 23 of the pipe 12 . the t - shaped fitting 22 shown is intended to be exemplary of just one type of such pipe fittings . as shown in fig4 , the cap 10 is generally a metal band having a circumference of any desired size so that it fits over a desired pipe or tube . the metal band 10 includes a first end 24 , a second end 26 , and a side wall 28 extending between the first end 24 and second end 26 . the width of the side wall between the first and second ends 24 and 26 may vary with the desired application . the side wall 28 also includes an inner surface 32 , an outer surface 34 . in the preferred embodiment , a lip 38 extends radially outward from the second end 26 . the lip 38 includes a radius 40 that forms a smooth transition with the side wall 28 . the side wall 28 also includes a plurality of inward deformations . as shown in fig4 and 5 , in the preferred embodiment , the inward deformations are a plurality of ribs 14 . the ribs 14 preferably extend across the substantial width of the side wall 28 , forming an indentation 42 in the outer surface 34 and a corresponding protrusion 44 on the inner surface 32 . the depth of the protrusion 44 may vary depending on the desired interference between the ribs 14 and the pipe 12 . in a preferred embodiment , three ribs 14 are spaced evenly about the sidewall 28 . however , any number of ribs 14 may be used , and the ribs 14 may have a different orientation , such as running circumferentially about the cap 10 . alternatively , the inward deformations may be a number of dimples , or a differently shaped inward deformation that creates a friction fit between the cap 10 and the pipe 12 . in the preferred embodiment , a positive stop flange 16 extends radially inward from the first end 24 of the cap 10 . the flange 16 preferably extends around the entire circumference of the cap 10 , having an inner surface 50 , and an outer surface 52 . the depth of the flange 16 is approximately the same , but not greater than , the thickness of the pipe 12 , so that the fitting 22 may still be inserted through the cap 10 and into the end of the pipe 12 . in another embodiment , the side wall 28 includes a hole 48 , or witness window . the hole 48 is proximate to the first end 24 of the cap 10 , allowing a user to view the pipe 12 through the window 48 when the cap 10 is placed on the pipe 12 . in operation , the second end 26 of the cap 10 is positioned proximate to the end 23 of the pipe 12 . a user will then slide the cap 10 onto the end 23 of the pipe 12 . as the cap 10 slides onto the pipe 12 , the lip 38 on the second end 26 of the cap 10 serves to guide the pipe 12 into the cap 10 , and then the ribs 14 engage the outer surface 19 of the pipe 12 , creating a friction fit between the ribs 14 and the pipe 12 for crimping . the pipe 12 is slid onto the cap 10 until the end 23 of the pipe 12 contacts the inner surface 50 of the flange 16 , and the pipe 12 is visible through the window 48 . the flange 16 prevents the cap 10 from sliding farther onto the pipe 12 , and the friction fit created by the ribs 14 prevents the cap from sliding off the pipe 12 without a force being applied by the user . once the cap 10 is in place , the insert 21 of the fitting 22 is inserted into the end 23 of the pipe 12 , and the cap 10 is crimped with a crimping tool to compress the cap 10 onto the pipe 12 , and compress the pipe 12 onto the fitting 22 . the above description is that of a preferred embodiment of the invention . various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims , which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents . any reference to claim elements in the singular , for example , using the articles “ a ,” “ an ,” “ the ” or “ said ,” is not to be construed as limiting the element to the singular .