Introducing the Phase 5 AR-15 Pistol Buffer Tube, a billet aluminum buffer tube, foam pad constructed of ultra-durable nitrile rubber, plus Mil-Spec end plate and castle nut. Buffer tube is compatible with Mil-Spec carbine buffer and spring, and the lower slot is machined to accept all Mil-Spec end plates and sling mounting accessories. FeaturesPistol Buffer Tube (PBT)Castle NutEnd PlateFoam Pad