Adapts 2 3S XH balance type packs into 1 6S XH output. Perfect for when your using 2 3S packs in series as a 6S pack. Allows simultaniously charge and balance on 6S charger. Note, packs should be each individually charged prior to installing this harness. After installation of balance adapter and putting outputs of packs in series, they can be charged and discharged as if they were a single 6S pack. Approximately 3" long.