TOPEAK REDLITE DX USBFour super bright L.E.D.s illuminate the way & make cyclists visible to motorists. Recharges via a computer USB (Universal Serial Bus) port. Constant or blinking modes Flexible strap 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/100hrs 4.5x 4.2x 2.8cm 38g (without battery)