This is an 8.4V 600mAh NiMH Receiver Battery Pack from ACE RC. FEATURES: AAA size cells JST 2-pin connector Round pack configuration INCLUDES: One 8.4V 600mAh NiMH reveicer battery pack REQUIRES: NiMH compatible charger SPECS: Length: 47.5mm (1.87") Diameter: 31mm (1.22") lmm 4.13.11 ir/jxs