Sol-Light 200 Light Cap Water Bottle 4 bright LEDs illuminate your water bottle into a solar powered lantern. Long-lasting, rechargeable & replaceable AAA NiMH batteries Fits all standard 2.25 diameter bottles, including Nalgene, and GSI Approximately 2 hrs. of direct sunlight will yield 1 hr. of operation; 12 hrs. of direct sun will fully charge the battery, providing more than 8 hrs. of light Integrated daylight sensor turns light off automatically if you forget to turn it off manually Weighs just 2.6 ounces. Weatherproof