This is the best selling Glock accessory and the one of most essential. Fits Models: 18/19/20/21/22/23/24/25/26/27/28/29/30/31/32/33/34/35/37 & 17 with three frame pins. This is a Glock OEM extended slide stop. It fits all 3 pin guns (the 3 pins are; trigger pin, locking block pin & trigger housing pin) except M/36,37,38,39. Also fits early G-19's with two pins. May be marked 2912,2912-2, or 2912-3. Does not fit early 17,17L,34 2 pin guns.