Sig Sauer MPX, Semi-automatic, Short Barrel Rifle, 9MM, 4.5 Barrel, Matte Finish, Black, Folding Stock, 35 Rounds, 1 Magazine RMPX-4B-9-35-SBR The choice of professionals worldwide, the MPX offers a closed bolt gas piston system that is ultra reliable and durable. The MPX now features the SIG folding stock which allows the rifle to fold into an ultra-compact size and be operable in the folded position. The MPX also features an updated M-Lok handguard which is available as accessories in multiple lengths for suppressor coverage. If you are looking for the ultimate modular sub gun, look no further than the MPX from SIG SAUER.