1as the built-in device generating electricity without the battery and any other power connets to water, led will emit the light. 2 when water flows down, the led will light instantly an automatically; Awhen water temperature is ¨¹32, green color will show automatically ; Bwhen water temperature is between 33-41, blue color will show automatically; Cwhen water temperature is between 42-45, red color will show automatically; Dwhen water temperature is above 46, red color will flash immediately. 3. This item will change its color by detecting water temperature. Packing detail:1 piece inner each color box 36 piece outer each carton