the only female bullet connectors in the circuit are located inside the shorty packs, you will be soldering a total of 4 male bullet connecters, 2 on the ESC leads and 2 on the pigtail between the packs
Connection 1 = Postive terminal from lower battery to Negative terminal from upper battery
Connection 2 = Positive terminal to Positive terminal on ESC
Connection 3 = Negative terminal to Negative terminal on ESC
All connections use bullets, depending on the brand of battery could be 4mm or 5mm...