This product replaces the magazine base plate and the internal locking sub-floorplate. They alter the capacity of the M/39 increasing by 1 round. The M27 & M/33 increasing by 2 rounds and the M/26 increasing by 3 rounds. They also provide extra grip length for better control and comfort. These units blend with the contours and texture of the handgun giving a factory appearance. They form the next logical finger positioning feature to provide control and comfort without sacrificing concealability
Put it on my glock 22 magazine, works great.