This laser engraved plug is designed to fit MODELS 17, 18, 19, 20, 21, 22, 23, 24, 25, 31, 32, 34, 35, 37, 38. Easy installation, just snaps right in. The Sure Plug 1 will NOT fit the SF models nor the Gen 4 Models. It will provide the user with the assurance that the magazine will not hang-up on the bottom rear of the magazine well by providing a smooth, rounded surface to guide magazines into place. The Flush fit of the plug also eliminates the possibility of snagging on the open cavity. The cavity on the backside of the handle (pistol grip), just behind the magazine well, is hollow and open at both the top and bottom. This opening can allow debris such as Dust, Dirt, Sand, Snow, Lint and Water to reach the trigger assembly and firing pin of the glock hand gun. The addition of this simple and inexpensive hand gun part can eliminate the potential problems created by this debris.