Four super bright L.E.D.s illuminate the way & make cyclists visible to motorists. Recharges via a mini USB (Universal Serial Bus) port on computer. Constant or blinking modes Flexible hook attaches to any tube Bulb: 4x super bright L.E.D.s Battery: 3.7V 240m Ah Lithium Ion Luminious Intensity (Whitelite DX USB): 5 (Lux/5M)/2 Lux/10M) Burn Time: 50hrs/100hrs4.5x 4.2x 2.8cm38g (without battery)