Sig Sauer MPX magwell was designed to meet the needs of competition shooters by enlarging the magwell opening where the factory didn't to ensure clean, fast reloads. The open front desgin allows you to grab the magazine without fear of pinching your fingers on the reload or having a load that is not completely seated. It works great with 10, 20 and 30 round MPX magazines. Machined from USA produced aluminum. It is attached with a friction fit on the larger opening magwells and includes a set screw for the undersized magwell that make installation a breeze.