The Phase 5 Hex-2 is an AR type Buffer Tube that starts with a hexagonal shape and the rear most portion is round. This tube was specifically designed this way to utilize the SB Tactical Pistol Stabilizing Braces that can accept a 1.2" round buffer tube (Not compatible with adjustable type braces like the SBA3/SBA4/PDW). The Hex-2 is a heavy-duty USA certified 7075 T7 billet aluminum buffer tube with the versatility to use the 3.5" Phase 5 nitrile Foam Pad (included) or a SB Tactical Pistol Stabilizing brace (sold separately). The Phase 5 Hex-2 Buffer Tube is a perfect component for any AR pistol build. The Hex-2-C Complete Package includes- Hex-2 buffer tube, castle nut, end plate, foam pad, carbine buffer and Phase 5 Enhanced buffer spring.