The whole kit-n-kaboodle ready to attach to your AR pistol or adapter. Taken to the range once. SIG SBX pistol brace, Radical Arms Buffer Tube, buffer* and spring, castle nut, and buttstock tube lock collar. *it's in the tube. $105, shipped in CONUS. Stolen from Amazon: * ATF has reviewed this product and determined that attaching the SBX to a firearm does not alter the classification of the firearm or subject the firearm to NFA control. SIG SAUER® introduces the SBXPistol Stabilizing Brace, a shooter's aid that is designed to maximize the potential of any buffer tube equipped pistol. This veteran-designed and U.S.-manufactured accessory enhances accuracy and reduces felt recoil. Made from high-quality, elasto-polymer, the SBX is manufactured to close tolerances and fits all pistols equipped with a buffer tube 1.0" - 1.2" in diameter. The Pistol Stabilizing Brace uses the operator's forearm to provide stable support, thereby minimizing accuracy-robbing spin and shift. A flexible cuff with two adjustable nylon straps allows the SBX to be custom fit to any user.