The Traxxas parallel connector lets you combine two 7.2 V NiMH batteries for extra-long run time in 1/16 scale vehicles. Dual-battery operation requires attention to precautions outlined in the model's owners manual. Follow all precautions to assure peak performance and reliability of your model and batteries. The Traxxas parallel connector is for use with (2925X) 7.2 V NiMH battery packs only.