Great quality muzzle brakes. Lock nuts and thread protectors. Both show 0.410bore diameter. Thread sizes are 0.475 id on the black one and 0.592 on the stainless one. No way to measure actual thread size. $30 per break. Small parts included. $30-10%=$27.00. Good quality brakes. I will ship for postage costs. Please see my other ads. Thanks, Joe.