Agency Arms P320 Compatible Magazine Extension Black 5RD. This base pad is specifically designed for the 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 P320 Compatible Magazine Extension: Manufacturer: Agency Arms Color: Black Fabric/Material: 6061 Aluminum Magazine Capacity: 5 Round Caliber: 9mm Luger Gun Make: SIG Sauer Gun Model: SIG Sauer P320 Features of Agency Arms P320 Compatible Magazine Extension Designed for the P320 17rd magazines Dot Matrix Panel for Marking Chrome Silicon Alloy Spring Increases capacity by 5 rounds (9mm) Extended Ledge for one-handed manipulations Compatible with the G17/17L 19X 34 45 Package Contents: Agency Arms P320 Compatible Magazine Extension Chrome Silicon Alloy Spring Set Screw What firearm models does the manufacturer say Agency Arms P320 Compatible Magazine Extension is compatible with? The manufacturer suggests that Agency Arms P320 Compatible Magazine Extension is compatible with SIG Sauer P320Agency Arms 25BP-3209-B17-5RD: P320 Compatible Magazine Extension Black