The Wii Balance Board is shaped like a household body scale, with a plain white top and light gray bottom. It runs on four AA batteries as a power source, which can power the board for about 60 hours. The board uses Bluetooth technology and contains multiple pressure sensors that are used to measure the user's center of balance—the location of the intersection between an imaginary line drawn vertically through the center of mass and the surface of the Balance Board—and weight.