Dimension: the overall diameter of the clock insert is 3-1/8 inch (80 mm) that refers to the front face outside maximum diameter including the colored bezel Mounting diameter: fit round hold diameter: 3 inch (76 mm); Mounting depth: 0.7 inch (18 mm), good for making crafts or replacing clock faces Suitable appearance design: two hands with black roman numerals on dial allow for easy reading Rubber band mounting system: equipped with rubber band gasket to securely hold the insert in place, which allows for slight irregularity in the hole Power: 1 x 1.5 V AA battery (not included)