Polymer magazine sleeve that permits use of a full-sized FN FNS 9/40 magazine in the FNS 9C/40C. Enables comfortable use of standard-capacity FNS 9mm and .40 S&W magazines with the compact pistol, increasing capacity and extending grip surface to mimic a full-size FNS. Provides an additional 3/4 inch of front strap grip space. Made to FN’s specifications and tolerances, using the same manufacturing and materials as the original equipment for a perfect fit and operation.