If you don't choose the correct backstrap to fit your hand size in the Gen4 GLOCKS, you could be causing yourself more recoil discomfort than is necessary. View attachment 223479 Note how the flat bone of my middle finger is perfectly in line with the flat portion of the bottom of the trigger guard on this older G19. The knuckle is out to the side of the trigger guard. View attachment 223480 Compare that image to this shot of a friend's newer Gen4 GLOCK 23 without a backstrap addition. You can see how the smaller circumference of the frame lets the large knuckle of my middle finger drift just far enough under the trigger guard to be hit upon recoil. I shoot .40 cal a lot, but 50 rounds of .40S&W wore that knuckle out. It might not be as noticeable in 9mm, but none of us have a GEN4 9mm yet to test. Adding the Medium backstrap to the Gen4 GLOCK moves my knuckle back out from under the triggerguard, and feels as comfortable as the GLOCKS i've been shooting for years. For folks with even longer fingers, the large backstrap might be needed to keep that knuckle out from under the trigger guard.