The Duo Charger for GoPro HERO4 Batteries allows you to simultaneously charge two GoPro AHDBT-401 type batteries from USB power sources. It is equipped with dual battery bays for charging one or two batteries at a time, with each bay featuring an LED indicator that displays charge status. Mini-USB and Micro-USB power inputs are provided, letting you connect the charger to a USB power source using the included Mini-USB cable or a compatible cable you already own.