Spike's Tactical Complete M4 Stock Kit, Includes ST-T2 Buffer, Buffer Tube, Buffer Spring, Castle Nut, End Plate, Fits AR-15 Rifles, Black SAK0701-K The Spike's Tactical M4 Complete Stock Assembly comes with everything you need to finish off the back end of your AR-15 lower receiver with top notch parts. This kit comes with a 6 position Mil-Spec Buffer Tube" M4 Collapsible Buttstock" Receiver End Plate" Castle Nut" Buffer Spring" and ST-T2 Heavy Carbine Buffer.