The Ghost Glock Gen 4 grip plug kit includes two plugs. One to be used with the back strap and another to be used without the back strap. The drop-in GHOST Grip Plugs are designed so that you can operate your Glock in a hostile environment, without the possibility of pistol fouling debris entering your pistol's mechanism through the grip opening behind the magazine well. The GHOST G-Plugs are designed to block the maximum amount of debris, while providing an improved chute to speed reloading. The GHOST G-Plugs also feature a bevel, assisting in magazine removal should a malfunction occur. To use, simply insert the GHOST Grip Plug that fits your application into the space Mfg: Ghost SPECS: Fits the following GEN 4 GLOCK19, 17, 22, 23, 31, 32, 34, 35, 37 & 38.DOES NOT FIT SF GUNS.