The Glock 21 Short Frame design reduces the circumference of the receiver, offering increased ease-of-use and control, especially to shooters with smaller hands. It features Glock's Safe Action system which provides a consistent trigger pull from the first to the last round. The three automatic independently operating mechanical safeties are built into the fire control system of the pistol. All three safeties disengage sequentially as the trigger is pulled and automatically reengage when the trigger is released. The frame is made of polymer with hardened steel guides. It features an ideal grip angle and low weight. The slide stop lever and the magazine catch are easily operated with the shooting hand. The advanced surface treatment of the slide results in optimal hardness by considerably reducing wear and tear and it makes it corrosion resistant, even when operating in saltwater conditions. The matte surface minimizes light reflection. The barrel is mechanically locked and cold-hammer forged. It also has the same advanced surface treatment as the slide. Its extractor serves as a loaded chamber indicator to comply with the laws of certain states and its position may visually and physically indicate whether there is a cartridge in the chamber of the pistol.