The Zippy Flightmax 1800mAh Transmitter pack fits snuggly into any Jr or Spektrum radio that takes a 8 x AA cell battery. With a capacity of 1800mAh this LiFePo4 replacement for your old NiCD or NiMH will last four to five times longer. Probably the best advantage with a LiFePo4 transmitter battery is that it will give a true voltage reading from start to finish which means you can say goodbye to the days where you thought your Transmitter was fully charged at home, only to find the voltage drop off rapidly when at the field. LiFEPo4 packs also feature a much lower self discharge rate than the NiCD and NiMH counterparts.With a nominal voltage of 9.9v, LiFePo4 cells are a closer match to the NiMH cells most radios were designed for. Spec.Capacity: 1800mAhVoltage: 3S1P / 9.9vDischarge: 5c Weight: 144g (including wire, plug & case)Dimensions: 100mm x 27mm x 33mmBalance Plug: JST-XHDischarge Plug: JR / Spectrum