The Apex Ultimate Safety Plunger for Glock is designed for use in the Glock 9mm, .40 S&W, .357 Sig caliber pistols and will smooth out the trigger take-up when compared to the original factory component. The Ultimate Safety Plunger maintains proper safety function, even when timing has been adjusted through the installation of aftermarket trigger systems. Fits 9mm: Glock 17, 18, 19, 26, 34, 40 S&W: 22, 23, 27, 35, .357, Sig: 31, 32, 33 Does not work with Glock Gen 5 models