EverActive CR1620 lithium battery - 5 pieces in a blister
Button batteries have a very wide range of applications:
Toys, calculators, music boxes, lamps, flashlights, LED decorations, pocket scales, bathroom scales, watches, bicycle computers, remote controls, measuring devices (e.g. electronic calipers, meters), medical devices (e.g. glucose meters), laser pointers, heart rate monitors, maintaining CMOS memory in computers and other devices and others.