An appreciable advancement in reliability and function has been achieved with these American-made magazines. Advancements in design and feed lip geometry have yielded enhanced function. Die-controlled tolerances are held to +/- .001" which is more than 75% tighter tolerances than magazines made to military specifications. Springs are made from aerospace-grade wire. Large view holes and numbers allow you to quickly determine how many rounds are in the magazine at a glance. Match grade magazines feature a fixed base plate.