Drop-in .22 LR conversion system comes fully assembled and ready to install in any semi-auto AR-15 to help you practice critical shooting skills with economical rimfire ammunition. Helps you concentrate on improving grip, sight alignment, trigger pull, and other skills without burning up expensive centerfire ammo.Simply replace the rifle's bolt and carrier with the Bravo .22 LR conversion unit, load up the included magazine with round-nose .22 LR ammo, and you're ready to shoot.Precision machined from high-grade stainless steel for reliable function in any mil-spec AR-15 rifle or carbine chambered in 5.56mm NATO, including most gas piston systems. Stainless steel bolt group Brass extension bushing.