Specifically sized for smaller devices, 390 coin or button battery is ideal for continuous use devices such as watches, small electronic toys, digital thermometers, glucometers, or heart-rate monitors. A watch cell is a small single cell battery shaped as a squat cylinder typically 11.6mm (0.456in) in diameter and 3.05 mm (0.120in) high – resembling a button. At BatteryDivision, 390 batteries are available in a variety of different leading brands, and can be purchased individually or at bulk pricing.