The Duracell Silver Oxide Button battery is designed to provide reliable power to specialty devices like watches, medical devices, digital thermometers, & other electronics. These batteries are guaranteed for four years in storage, so you can be confident these batteries will be ready when you need them. From storm season to the holidays, Duracell is the number one trusted battery brand. Battery Type: Silver Oxide; Battery Size: 309 / 393; for Use With: Everyday Electronic Devices; Voltage: 1.5 V.