Very cool and useful product!! - It's ultra thin At 15mm it's thinner than the MacBook Air - It's powerful BatteryBox Slim has 89Wh capacity, a 48.3% improvement over the original BatteryBox's 60Wh capacity - It's future proof Whether you own a new USB-C device, a Chromebook, a MacBook, or a Windows laptop. The BatteryBox Slim comes with a USB-C port and has several cables each compatible with all sorts of laptops.