The DigiRoller Plus III measuring wheel can measure distances and calculate area, volume and perimeters based on stored data. The simple keypad unit stores measurements for later use and can switch between U.S. and metric units. The gear drive is sealed to prevent debris from damaging the device, and it has a built-in kickstand for storage. The DigiRoller Plus III runs on a standard 9-volt battery. Calculated Industries; www.calculated.com