When engaged in Force on Force Training, Ultimate Training Munitions (UTM) optional polymer safety magazines provide a clear and safe indicator to Instructors, Users, and Bystander’s showing that weapons are in “training mode”. The M16/M4 Blue Mag was specifically designed to prevent the loading of a M855 Round for the US Military. Rated at 99.8% reliable this magazine provides a clear additional agency indicator that your weapon is in safe NLTA training mode. Unsurpassed levels of magazine-weapon reliability and performance. One of the most durable magazines on the market. The UTM Training Ammunition can be used in standard weapon magazines but UTM strongly recommends the use of the UTM Blue Safety Magazine for optimum Safety, Reliability, and Performance.