Get fit with Misfit Flash, a sleek, sporty fitness tracker that measures your activity and sleep, syncs with your smartphone, and comes in a variety of colors. Press Flash to see a halo of lights that shows your progress toward your daily activity goal and tells time. Flash never requires charging and is made of rugged, yet ultra-comfortable soft touch materials.We strongly recommend customers to use two battery brands which are Panasonic and Energizer.If the product is defective submit a request at firstname.lastname@example.org.For more information on how to replace a battery please visit http://misfit.com/go/flash. Please follow the below steps to sync the app: Reboot the phone, Turn OFF then turn ON Bluetooth from the phone’s Settings menu and Right before syncing, try press the Flash to turn the light on. It should make syncing much easier.