NiteRider's Lumina 600 OLED guides you safely home. This bright light puts out up to 600 lumens for up to 21 hours and weighs in at only 172 grams! It attaches easily and fits on handlebars up to 31.8mm in diameter. There are five modes to choose from: high, medium, low, energy-saving walk, and flash. You can charge it off a computer's USB port and, should you throw it in a bag for later use, the Lumina's lock out mode ensures it won't accidentally turn on and waste battery life. The OLED displays battery-power percentage remaining, battery-power time remaining with selected light-level mode, and Light Mode Level.