The FAB Defense Magazine Extension is a magazine floor-plate replacement that adds 4 rounds of capacity in a magazine. Special ergonomic design enables secure manipulation of the magazine and a full grip on the weapon when the magazine is in use. FeaturesEnables a full grip on the handgunContoured finger indents for a firm grip during magazine manipulationInnovative spring plate allows the use of the original magazine springFiberglass reinforced polymer construction Note: In 2021 Glock added an extra Coil to their magazines so you can only fit 3 extra rounds