The Phase 5 Hex-2 is our newest AR type Pistol Buffer Tube. This tube has been specifically designed to utilize the Sig Sauer SB15 Pistol Stabilizing Brace. The Hex-2 is a heavy duty USA certified 7075 T7 billet aluminum pistol buffer tube with the versatility to use the Phase 5 nitrile Foam Pad (included) or the SB15 Pistol Stabilizing brace (sold separately). Working closely with Sig Sauer the Phase 5 Hex-2 was a special project that involved a number of firearms instructors, law enforcement professionals and AR Pistol enthusiasts alike. While asking questions along the way and updating the design based on the recommendations given by all; the Hex-2 has become the perfect component for any AR pistol build. The Hex-2 even in its most basic package includes a castle nut, end plate and foam pad. Length of pull (LOP) measurement with Sig Stabilizing Brace installed: Measured from the back of the lower receiver End Plate to the very end of the Sig Brace is 9 1/2 inches.