Tested and proven by the US Army and Navy. Will not loosen under sustained fire. Will not white out PAS13 thermal night sight. Can be installed on older M2HB weapons. Improves systems accuracy. Made from ordanance grade 8620 and 1144 Stressproof®. This model includes a redesigned coupler made from Fatigue Proof steel, M80HT heat treated. Weight (including split rings): 2.39 lbs.