10cm small female RC connector to large male cable. If you have an AEG that is built to use a small / stick battery with a small type male connector, then this cable will allow you to extend the wire outside of the gun so that you can connect a large type battery (with a large female connector). Note that if your gun's design does not have enough room to store the large battery internally, then you will need to purchase a battery bag / pouch to hold the battery on the outside of the gun.
Disclaimer: All aftermarket upgrade parts require necessary skill or modification to install and assemble, please consult with your airsoft technician if needed.