Perfect for any rail system, these low profile gas blocks are the ideal companion for barrels with a standard diameter gas journal. Made from high-strength steel, all Creative Arms LLC. gas blocks are a matching black luster to their barrels. The gas block clamps on to the barrel using 2 allen keys on the bottom of the block. Creative Arms LLC. highly recommends the use of Loc-Tite or similar thread-locking compounds. Gas blocks will get very hot, so pick a compound according to your intended use of the firearm.