Battery-Free, Hydro-Powered Non-polluting Outdoor Camping Light for Outdoor Activities, Lasts up to 288 Hours. Easy to Use and 2 Light Modes: Open the seal. Add 15-40 grams of salt(more salt, more brightness). Add water to the water level line. Shake it after sealing and wait for 15s. Turn on the red switch and it will work immediately. 2 light modes adjustable: continuous light and flash.