Decodyne Math Clock - Discontinued by Manufacturer A UNIQUE WAY TO TRACK THE HOURS Instead of Roman numerals or traditional numbers, this clock has a different equation at each demarcation PERFECTLY SIZED Clock measures 11-1/2 inches in diameter and is easy to spot from afar GO WITH EVERYTHING DESIGN Black and white color scheme makes the clock look like a chalkboard and will complement any color palette GREAT GIFT IDEA Give one of these wall clocks to a math teacher, engineer, mathematician or anyone who just loves numbers NO CORDS OR WIRES Clock runs on one AA battery (not included)