Sig Sauer Magazine, 9MM, 20 Rounds, Fits All Generations of MPX, Black, Polymer 8900828 The SIG SAUER enhanced factory MPX 20-round 9mm magazine combines the best of metal and polymer designs. It features metal feed-lips for enhanced durability and a robust yet lightweight polymer body for shape retention. The SIG SAUER MPX Magazine is the result of a 2-year design project to create a magazine that met all of the SIG quality and reliability standards while providing even higher performance in the MPX platform.