For spelunkers, the YUKON EXTREME offers 4 levels of brightness, a compact external battery pack and up to 200 hours of burn. The Yukon Extreme is by far the most versatile, longest-burning headlamp in the Princeton Tec line. You have the ability to switch between a piercing, high-power Xenon bulb for long-range, high-intensity requirements and three regulated Ultrabright LEDs for camp activities and casual trail navigation. The advanced circuit system of the Yukon Extreme allows you to choose from four brightness levels of light output to satisfy mountaineers, adventure racers, cyclists, cold-weather climbers, backpackers and campers. The compact, remote, 8-AA battery pack can be clipped to your waist or other gear to minimize the weight on your head. In cold weather, wearing the battery pack under clothing, close to your body, will increase alkaline battery efficiency and run times. The Yukon Extreme is designed to work with alkaline, lithium, and rechargeable batteries