of the patient such that the injection device 10 is generally perpendicular to the skin of the patient and the forward tip 34 of the needle cannula 16 is adjacent to the skin of the patient the holder 200 is then displaced toward the skin in generally perpendicular relation thereto such that the forward tip 34 punctures the skin and enters the patient 39 s body the index finger of the user 39 s hand is then moved into contact with the pusher cap 252 and the pusher cap 252 is depressed to advance the pusher stem 258 into the reservoir 12 the advancement of the pusher stem 258 into the reservoir 12 results in movement of the stopper 24 in a proximal to distal direction and fluid injection through the needle cannula 16 the pusher stem 258 is advanced a distance sufficient to cause the stopper 24 to traverse the longitudinal length of the reservoir 12 this advancement defining the injection stroke at the end of the injection stroke the cap wall 256 is inserted into the insertion gap 265 between the pushbutton 212 and ring lever 246 as shown in fig5 preferably the cap wall 256 has sufficient longitudinal length to be interposed between the pushbutton 212 and the ring lever 246 consequently the radial clearance between the pushbutton 212 and the ring lever 246 is eliminated prior to.