Replacement floorplate set to increase the capacity on select Mec-Gar Glock Series of magazines.Contains: 1 - Polymer "Plus-2" magazine extender 1 - Phosphate steel locking plate heat-treated 1 - Type D music wire spring 1 - High-visibility green polymer followerTHIS ITEM WILL ONLY WORK ON THE MAGAZINES LISTED BELOWMec-Gar Magazine for Glock 17 9mm 18rd - MGG171800A - Adds 2 roundsMec-Gar Magazine for Glock 17 9mm 10rd - MGG171000A - Does not add capacityMec-Gar Magazine for Glock 19 9mm 18rd - MGG191800A - Adds 2 rounds