?Avoid the risk of hot-water burns, even at night. This special light adds color to the water's stream to alert you to its temperature. When cold, the water glows a neon, plasma-like blue. It warns you with a luminous red light when water gets hot. Function is activated by water pressure so they only shine when the tap is on. Lights deactivate a few seconds after tap is turned off, so lights can never be left on overnight. Easy to install, the attachment adapts to most standard fittings. Includes faucet light, 2 adaptors and 3 cell batteries. Measures 2 3/4"H x 1/2"Diameter.