Check-Mate’s line of 2011® compatible magazines are made from the highest quality American milled stainless steel. Every tube is through-hardened for exceptional strength and durability. Tubes are polished inside and out to eliminate drag. The follower is designed featuring Check-Mates anti-friction self-lubricating polymer for exceptional feed and function with every round. Check-Mates high-performance springs offer high quality, outstanding reliability, and exceptional spring endurance.