ProMag Ruger MK III magazine bodies are constructed of high carbon heat-treated steel and TIG-welded for strength. The springs are precision wound using heat-treated chrome silicon wire. Bases & followers are injected molded from polymers selected for their unique durability. Quite simply, Promags's products are able to withstand years of constant use and still be able to perform without the slightest hint of difficulty.
ProMag magazines include a lifetime guarantee. If you ever have a problem with their magazines; simply return them to ProMag for replacement.