This small but mighty M1 flashlight is the one model in this series that calls for CR123 batteries. Not only do CR123 batteries have an extremely long shelf-life (10+ years) and maintain high voltage for plenty of power, they also work well in extremely cold temperatures where standard batteries can drain quickly. The M1 is a great lightweight and powerful flashlight with the means to take on the elements when necessary. Specifications - Brightness: 150-27 lumens Beam: 150-65 meters Run Time: 3-5.5 hours.