The NEW Magblock for Glocks MCL (Magazine Capacity Limiter). Unmodified this limiter fits the Glock 17 9mm 17 round magazines. This block fits into the follower and slides into the spring converting the magazine to hold only 10 rounds. Patented design offers Pre-molded levels to fit all other current 9mm and .40 Glock magazines. This requires some cutting and filing. A 15 round option is even included. Does not affect reliability or magazine function. No increase in spring pressure which would reduce spring life. Compatible with the shown follower type only. This follower type is present on almost all metal lined Glock magazines. Can be used in Korean and original Glock magazines.