Maxell is the first company in Japan to successfully market button-type silver oxide batteries and has many years of experience and know-how. Button-type silver oxide batteries such as this 391 battery are characterized by high-energy per unit volume and stable operating voltage. As a result, they are used as a power source for applications such as quartz watches, and in recent years their use has expanded to medical devices and BLE devices. This Maxell battery is ideal for 391 battery replacement.