Agency Arms Sig Sauer P320 9mm +5 Pistol Magazine Extension Red 5. This base pad is specifically designed for they 17rd magazines and is compatible with the Agency Arms X-Series Magwell and the factory magwell from SIG. (THIS BASE PAD IS NOT COMPATIBLE WITH THE AXG MAGWELL) Specifications for Agency Arms Sig Sauer P320 9mm +5 Pistol Magazine Extension: Manufacturer: Agency Arms Magazine Capacity: 5 Round Caliber: 9mm Luger Gun Make: SIG Sauer Gun Model: SIG Sauer P320 Features of Agency Arms Sig Sauer P320 9mm +5 Pistol Magazine Extension Dot Matrix Panel for Marking Chrome Silicon Alloy Spring Increases capacity by 5 rounds (9mm) 4 round (.40s&w & .357) Extended Ledge for one-handed manipulations Package Contents: Agency Arms Sig Sauer P320 9mm +5 Pistol Magazine Extension What firearm models does the manufacturer say Agency Arms Sig Sauer P320 9mm +5 Pistol Magazine Extension is compatible with? The manufacturer suggests that Agency Arms Sig Sauer P320 9mm +5 Pistol Magazine Extension is compatible with SIG Sauer P320Agency Arms AGEBP-320-RONIN: Sig Sauer P320 9mm +5 Pistol Magazine Extension Red