Never again worry about over-filling your beverage glass or coffee mug. Simply hang the handy Dual Sound Liquid Level Indicator on the lip of your cup, glass or mug and pour with complete assurance. When filling a cup/mug, as you reach the top you will hear a series of warning beeps telling you to slow down. The sound shifts to a continuous tone when the top level is reached, indicating the cup is full and you should stop pouring. Uses one 9-volt battery (included.)