The FNX Magazine Base Pad Extension adds two and a 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? Apexs mag extension leaves enough space for 2 additional rounds to be loaded, but also 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.Features :Fits FNX 45 model pistols.+2 Rounds.Maintains function of the slide lock after the last round is fired.Finger grooves on the perimeter and front corner finger grooves make gripping the base easy.Machined from aluminum and Black Type III Hardcoat Anodized for durability. Single Set screw keeps mag extension snuggly in place and allows for ease of disassembly. Easy to install