This is Li-Po Battery Pack 7.4V 4,000mAh - the lithium polymer battery pack of 7.4 volt operating voltage and 400mah battery capacity. The lipo battery dimension is 5.0 x 65 x 110mm. Up to 1,000 times of charging time. This is low internal resistance battery to consider. The battery dimension you should consider too, is this match with your rc battery slot?