Yueton&reg; Temperature Sensor 3 Color Changing LED Light Faucet for Bathroom / Kitchen (Silver) No batteries and external power supply, it will illuminate after water flows down. You may be puzzled with the water temperature unless you touch it, now with this device this problem is solved Color's change remind you the water's temperature. Transforming the stream of water into a beautiful waterfall of light. Offer you a delight & wonderful experience.