This battery adapter connector allows you to plug two batteries with XT60 style connectors together in Series to power a single speed controller. This adapter is built with the newest AMASS brand XT60 connectors to be able to handle the higher currents of larger aircraft. To use this adapter, both batteries must have the same mah capacity. For example, two 3-cell 2200mah batteries can be connected together to form a 6-cell 2200mah battery. You can also use cells with different number of cells, as long as the capacity is the same. You could take a 2-cell 2200mah battery and connect it with a 3-cell 2200mah battery to make a single 5-cell 2200mah battery.