Ultimate Arms Gear Safe-Draw Guard Lock Kit for Handguns Pistols Glock 17 18 19 20 21 22 23 24 25 26 27 29 30 31 32 33 34 35 37 38 39 40 41-1 Lower Base Block Package Includes: 1 Lower Block, Black (Upper Locks Pressure Weights Sold Separately) Bottom Lower Block Frame Is Reusable. Fits Glock Gen 3-4 But Does Not Fit Glock 30S, 36, or 42. Will fit on some Gen 1-2 pistols, but may slide on the guard. This product may prevent a small child from being able to pull the trigger on a loaded gun, increases the force required on the first trigger pull and makes the gun more child resistant. The gun can still be accurately shot by pulling the trigger with more force. Easy upgrade for Glock. Reliable and rugged polymer construction similar to Glock frame material. No gunsmithing or replacement of factory parts. No switches or buttons. Just aim and squeeze.