Introducing the LightCap.This isn't a Nalgene bottle, although it looks similar (and it's only 4.5 oz heavier than a Nalgene). This Polycarbonate bottle has a cap with an embedded solar panel, charging system, sealed Ni-Cad battery and a white and red LED light. Clip this to your pack, or leave it in the sun by day, and at night you have a lantern for use in your tent or around camp. The panel also has a daylight sensor, which prevents the light from running while the panel is actively charging. The red led on a full charge will run 16-18 hours, and the white LED will run 8-10 hours. We've tested these, and on a dark night they are decent task lighting. You might be able to read by the light given off, but our aging eye grew tired. Neat-o product and not gimmicky at all.