These Grip Extensions replace the magazine base plate providing better comfort and control by adding approximately 1/2 inch of gripping surface. They do not alter the capacity of the magazine. An optional filler piece is provided for Glock Gen 5 models with the semi-circular cut-out in the lower front area of the grip body. This product will only work on magazines equipped with double notches for the ambi magazine release.(Gen 4&5 magazines) *NOT FOR 10-ROUND 9mm MAGAZINES*