Armageddon Tactical crush washers have a unique radial groove cut into the inside diameter which allows the washer to collapse uniformly and with even torque. The washers fit 1/2-28 barrel threads and will collapse 1 full turn while providing 15-20 lb. ft. of torque throughout the entire range. This produce is machined from 4140 steel and coated with black oxide. Shipped in packs of 5 with installation instructions. USPS First Class Parcel shipping included in price.