BL21 bicycle head light use a high performance CREE XM-L2 LED generates max 900lm output. The lamp integrated one 2500mah 18650 battery to support at least 3 hours non-stop lighting. Areo-space aluminum material with hard anodized surface finish make the light much more durable. Easy switch operation, quick click to switch high, med, low strobe, SOS modes after turn on the light. The indicator shows the battery power everytime. IP65 waterproof assure you can ride at rainning condition.