The JP Extended Magazine Release Button comes preinstalled on a standard Glock magazine release with a 4-40 flat head screw and gives just the right height and offset extension for speed reloads without shifting the strong hand's grip on the gun. The back of the button is serrated to secure it against the stock mag release once installed. This simple part is a must for the competition grade Glock. Available for large frame Glocks. The small frame mag release has been discontinued. The large frame release is for 10mm and .45 cal guns. Does not work with Gen 4 frames.