The MagPul BAD (Battery Assist Device) extended bolt catch attaches to the standard AR-15 bolt catch with a backplate and screw, making for easy installation with zero permanent gun modifications. The BAD features a thin, low profile to help minimize snagging, yet offers lightning fast reloads by allowing the bolt catch/release to be engaged using the trigger finger within the trigger guard. Machined from 6061 billet aluminum for strength and durability. NOTE: The BAD is compatible with all standard, mil-spec forged AR-15 upper/lower receivers, as well as HK416, Vltor VIS/MUR, Larue Stealth, and many other billet upper/lower combinations. It is NOT compatible with LR-308, SR-25, AR-10 or other .308 AR-style platforms.