The SIG P320 9mm +5 base pad for 17rd magazines. 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)Machined from 6061MIL-A-8625 Type 3 Hard AnodizedDot Matrix Panel for MarkingChrome Silicon Alloy SpringIncreases capacity by 5 rounds (9mm), 4 round (.40s&w & .357)Extended Ledge for one-handed manipulationsMADE IN USACANNOT SHIP TO CA, HI, MA, NY, NJ, CO, VT, MD