The AR-15 magazine catch assembly is the group of parts that secures the magazine in the lower receiver and allows quick reloads. It includes the magazine catch, magazine catch spring, and magazine release button. The catch locks the magazine in the mag well, the spring holds it under tension, and the release button drops the magazine when pressed. The assembly fits all mil-spec AR-15 lower receivers and works with standard AR-15 magazines and lower parts kits.