Pearce Grip Grip Insert, Fits Glock Gen4, Mid/Full Size, Black PGG4MF This unit installs in the bottom rear cavity of the frame utilizing the lanyard hole for retention. Fits model M17" 18" 19" 22" 23" 24" 31" 32" 34" 35" 37" 38 and 45. This product will only fit Generation 4 and 5 frames. Allows for use of factory interchangeable backstraps.