The Phase 5 Hex-2 is an AR type Buffer Tube that starts with a hexagonal shape and the rear most portion is round to accept our foam pad. 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). This design, based on the recommendations from our customers, makes the Phase 5 Hex-2 Buffer Tube is a perfect component for any AR build.The Hex-2-C Complete Package includes:Hex-2 Buffer TubeCastle NutEnd PlateFoam PadCarbine Buffer - Standard 3ozPhase 5 Enhanced Buffer Spring***NOT COMPATIBLE WITH ADJUSTABLE BRACES/PDW