It can improve exercise and will help you maintain vitality when you see the clock . It's also the perfect office clock for an , mathematician, or anyone who works with numbers. Name: Wall Clock Material: acrylic Color: Black Power supply: 1 x AA battery (not included). Diameter: . 30 cm. Package Contents:1pcs x wall clock Only the above package content, other are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm. The black dial looks like a chalk board. Each is painted to white chalk. As the clock is ticking, the hands move around the dial, showing the time of day through a different problem for each hour. It's a unique and way to keep track of time. This wall clock is a and challenging exercise. This analog display wall clock is made of high quality acrylic material with white letters and numbers, perfect for classroom or office. Instead of using Roman numerals or numerals, this wall clock has a different on each delimitation. It has to be a fashionable decoration for the wall, especially for the classroom, office and study, and an for your friends or their children.