Strike Industries Extended Bolt Catch, Black SI-AR-XBC The SI-XBC Extended bolt catch is a heavy duty" go-fast addition to the SI line of enhanced parts. Under high stress situations" the oversized bolt release lever aides in rapid thumb or palm engagement" even with gloved hands. The lever is reinforced for increased durability and impact resistance. Made from solid precision cast (not MIM!) steel" and hardened according to military specifications" the SI-XBC is a simple solution that ensures a lifetime of hard use.