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.Finish: BlackType: Buffer Tube KitModel: Hex-2Material: Aluminum