A magazine originally designed to hold 40 rounds of ammunition that has been modified to hold a maximum of 10 rounds. These magazines have a 40 round body and have been blocked to 10 rounds in order to comply with magazine limit restrictions in California, New York, Connecticut, DC, Maryland and Massachusetts.
10/40 mags are modified to hold a maximum of 10 rounds to comply with magazine limit restrictions in several states. The 40 round magazine body retains the original look, and can be easily grasped for quick magazine changes. 10/40 mags are modified for AR15 and M4 rifles.