LBE Unlimited is a quality manufacturer of AR-15 parts and accessories. This particular item is an AR-15 pistol buffer tube receiver extension kit. This Complete kit can be used as a replacement unit or as a spare for a new build. This unit comes with all the parts you need to assembly the stock section of the lower receiver. This kit along with it's components are made right here in the USA. Features: Black finish AR-15 Mil-Spec stock assembly kit Includes buffer tube, castle nut, endplate, buffer and carbine spring