Experience unmatched reliability with the ProMag Industries SIG-21 Magazine, built in the USA for optimized performance. This magazine is engineered with premium materials, ensuring durability and effortless loading. With meticulous attention to detail at every stage of production, the SIG-21 meets the highest quality standards. Heat-Treated Chrome Silicon Wire Spring Manufactured & Assembled in the U.S.A. Easy Loading Rugged Construction Invest in longevity with the ProMag SIG-21, your trusted companion for superior firearm operation.