CycleBeam 900 Lumen Long Run Time Bike Light with Warning Blink Primary Light: Extremely bright CREE XM-L2 T6 LED bulb Secondary Light: Twelve (12) additional micro LEDs surrounding the primary LED can be used in a constant beam mode (very low power draw) or blinking mode ( for safety). Large Battery Capacity: Light weight 33 WH Li-ion battery pack is included. Long Run Time: Light for up to 15 hours depending on which brightness level you choose. (4 hr at High, 8 hr at Medium and 15 Hr at Low). Weather Resistant: Tough, water-resistance, aircraft-grade aluminum housing is designed for efficient heat dissipation (longer battery life).