Perfect for any rail system, these low profile gas blocks are the ideal companion for barrels with a standard diameter gas journal. Preassembled with a gas tube properly mounted and made from 4140 high-strength steel, all Creative Arms gas blocks feature a black Ultra Ox nitride corrosion resistant finish . The gas block clamps on to the barrel using 2 allen screws on the bottom of the block. Creative Arms highly recommends the use of high temp Loc-Tite, Rock Set or similar thread-locking compounds. Gas blocks will get very hot, so pick a compound according to your intended use of the firearm.