Got em, love em, on my Gen 4 19. Had problems with slide bite, and was ready to trade for a Gen 3. Put the smooth one on, problem solved. Money well spent. People with BIG hands use the large backstrap. The small beavertail on the Gen 4s rubs the knuckle at the base of the thumb raw. Bad design, Glock. These fix the problem. Wanna kill these ads? We can help!