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 follower THIS ITEM WILL ONLY WORK ON THE MAGAZINES LISTED BELOW Mec-Gar Magazine for Glock 17, 9mm 18rd - MGG171800A - Adds 2 rounds Mec-Gar Magazine for Glock 17, 9mm 10rd - MGG171000A - Does not add capacity Mec-Gar Magazine for Glock 19, 9mm 18rd - MGG191800A - Adds 2 rounds