ETS mags won't crack or break, are resistant to heat, cold, UV and harsh chemicals and won't become brittle over time. Their mags come with enhanced features like non-tilt followers, creep-resistant feed lips and clear body allowing you to see count and ammo type, leaving nothing to chance. Fits the Sig Sauer 9mm P320 Extended 21-round capacity Base plates interchangeable with ETS line of 9mm double stack magazines Easy disassembly with their specially designed base plate Ergonomically designed floor plate makes it easy to grab from mag pouches