LBE Unlimited AR15 Pistol Buffer Tube Kit, Buffer Tube, Recoil Spring, Castle Nut, Receiver End Plate, Recoil Buffer, Black PBUFKT-BLK 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 kit includes a pistol buffer tube" carbine recoil spring" standard carbine recoil buffer" receiver end plate and castle nut. LBE Unlimited is a leading producer of US-Made gun parts and accessories.