No batteries needed in our energy-saving Digital Water Powered Clock. Simply pop off the cap, add water, and it will magically tell time. Why go through countless batteries that are harmful to the environment when you can power your home or office clock with natural resources Available in a variety of vibrant colors, this perfectly sized clock will conveniently fit on any desktop, tabletop or bedside table without taking up much space. Easy to read, our fun, unconventional clock features large numerals. A great gift for any gadget lover, the mechanically minded or environmentalist, this unique water clock is sure to impress young and old! Plastic. Holds up to 4-1/2 ounces of water. Please choose Grey, Yellow, Green, Red or Blue.