This polymer magazine sleeve permits the use of a full size FN FNS 9/40 magazine in the FNS 9C/40C. This permits additional ammo capacity, as well as lengthens the grip of the pistol. The full size grip permits better control of the handgun after recoil, and permits a more confident draw. The sleeve is a perfect match to the firearm grip, and is textured for a sure grip under all conditions.