This product is used to charge 2 packs of 3S Lithium batteries at the same time with GTP-A8, A6, iMAX B5, B6, B6AC, B8, EC POWER S6 etc charger. TWINS adapters are suitable for charging two packs of 3S Lithium battery at the same time. If you charge only one pack of 3S Lithium battery, please plug the battery directly into the balancing port of the charger. It will extend the charging time when you charge two packs with different capacity or different discharging degrees. Please use the batteries which are the same in capacity, discharging degrees, facotory and discharging rate with TWINS adapters.