Specifications: Size: 12 inches, diameter 30 cm, thickness 4 mm Material: Environmental protection MDF covered with crystal foil Color black Power supply: 1 AA carbon battery Packing list: Wall clock * 1 Material This analog display wall clock made of high quality acrylic material with white letters and numbers, ideal for classroom or the office Special design The black clock face is designed to look like a blackboard, with each math equation looking like white chalk. Instead of traditional numbers, this wall clock has a different equation for each delimitation. Funny Mathematical When the clock is ticking, the hands move around the dial, telling the time indicated by a different math problem for each hour will. This unique wall clock is a fun and challenging brain exercise. Fashion Decoration A very fashionable decoration for the wall, especially for the classroom, office and study, and an ideal gift for your friends or children Application Ideal for the budding math student or anyone who wants something different in a watch. For classroom, study, living room, nanny bedroom, office.