NiteRider Lumina 350 Cordless Headlight Li-Ion battery charges in only 4 hours via USB cable plugged into your PC Built-in indicator light switches from red to blue when the battery is fully charged High-powered Cree LED produces more light with less power and less heat Custom made reflector and Borofloat lens work together to minimize light transmission loss and maximize light output for excellent optical clarity -- superseding internal reflectors or standard glass lenses Runtimes: 2 hours High (350 lumens), 4 hours Medium (200 lumens), 6 hours Low (125 lumens), 21 hours Walk (30 lumens)