Cree T6 Bulb. Max output 1800lm is rated by manufacturer * Battery: 1x 18650 3.7v battery (NOT included) DO not use 2x CR123 batteries! * Material: 6061T Aluminium; Size(mm):120 x 33(bezel)/26(body) * 3 Mode: High / Low / strobe * Working voltage:3.6v-4.2v; 18650 battery is a great choice, need to purchase separately.