Only the finest polymers go into our polymer magazine bodies. The springs are precision wound using heat-treated chrome silicon wire. Bases and followers are injection molded from polymers selected for their durability. Then, each and every step of the assembly is checked and double-checked in order to maintain the same consistent level of quality. We're so sure of how good ProMags are, we've warrantied them for as long as you own them. Each and every ProMag is made right here in the U.S.A.