LBE Unlimited AR15 Milspec Buffer Tube Kit, Buffer Tube, Recoil Spring, Castle Nut, Receiver End Plate, Recoil Buffer, Red MILBUFKT-RED This LBE Buffer Tube Kit includes a six position mil-spec diameter buffer tube" carbine length 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.