The LBE AR-15 pistol buffer tube receiver extension comes with no provision to mount a buttstock” allowing your pistol build to remain legally compliant. It features a foam end cap that covers the tail of the buffer tube for use in attaining a more comfortable cheek weld. This buffer tube can be used as a replacement unit or as a spare for a new build. This unit is pre-threaded and will install easily to any standard pattern AR-15 lower receiver. LBE Unlimited is a leading producer of US Made gun parts and accessories.