PortableBuilt-in 1000mAh battery, you can carry it anywhere, key chain design easy hook on the bag, extend your Apple Watch battery life in an emergency when the watch power low,about 2.5hours will let your watch give full power. it could charge the watch 1-1.5times when this charger fully charge. convenient for your purse pocket bag RechargeableThis is a re-charger, lightweight and compact design enough for weekend getaway, combine your large power bank and others USB charging device, you can recharge this charger after its power transfer to Apple Watch, the charger will be fully charged within 1.5hours. easy to use when traveling