Power up your smartwatch with this UltraLast smartwatch replacement battery. The precise design provides compatibility with select Fitbit smartwatch devices, providing dependable power for lasting use. A convenient rechargeable format helps extend the life of your device, and the simple configuration makes this UltraLast smartwatch replacement battery easy to install. Lithium-polymer battery Supplies reliable power to Fitbit Charge 2 smart watches. 3.7V of power Delivers a reliable, long-lasting charge to your electronics. Rechargeable design Delivers power efficiently.