Shop › AGENCY MAG EXT SIG P320 17RD +5 BLK AGENCY MAG EXT SIG P320 17RD +5 BLK $49.00 Agency Arms +5 Magazine Extension, Fits Sig Sauer P320 Magazines, Anodized Finish, Black, Aluminum Construction BP-320-BLK Add To Cart Added! Agency Arms +5 Magazine Extension, Fits Sig Sauer P320 Magazines, Anodized Finish, Black, Aluminum Construction BP-320-BLK