The Apex Tactical FNX Magazine Base Pad Extension adds two and half (2.5) rounds to the existing standard capacity magazine for the FNX 45 model pistols. "Why is it 2.5 rounds, not 2 and not 3," you ask? The FNX mag extension provides space for 2 additional rounds to be loaded, and it leaves enough space for the stack to further compress the magazine spring to allow a fully loaded magazine to be seated with the slide in battery. FeaturesAdds 2.5 rounds of additional capacity to your magazineMaintains function of the slide lock after the last round is firedFinger grooves on the perimeter and front corner finger grooves makes tripping a hard mag easyMachined from aluminum and Black Type III Hardcoat Anodized for durabilitySingle set screw keeps mag extension snugly in place and allows for ease of disassemblyEasy to install