The Apex Tactical +2 Magazine Extension adds two rounds of capacity to FN FNX-45 magazines. It replaces the factory floor plate, so the magazine body you already own stays in service with more rounds on board. The extension is machined aluminum with a Type III black hardcoat anodized finish. It preserves last-round slide lock, so the slide still locks back on an empty magazine the way it does with the factory floor plate. Features: Adds 2 rounds to FN FNX-45 magazines Replaces the factory floor plate Machined aluminum base pad Type III black hardcoat anodized finish Preserves last-round slide lock Fit: FN FNX-45 and FNX-45 Tactical magazines. This extension is FNX-45-specific. It does not fit FNP or FNS magazines. After you install it: load the magazine to full capacity, seat it in the pistol and run it to slide lock with your carry ammunition before you depend on it. Check your state and local magazine capacity limits before you install a capacity extension.