10cm small male RC connector to large female cable. If you have purchased a battery charger that comes with a big connector, and need to use it to charge small batteries with the small Tamiya style female plug, then this is the wire you need.

Alternatively if you have a gun that comes with a SMALL female Tamiya style connector, and you wish to use a bigger battery that has a LARGE male connector - then you can use this adapter cable (assuming your gun's stock has enough space for the bigger battery and this connector cable)