[supermaxx4190]

it means 2 cells wired in series, so 3.7 volts plus 3.7 volts = 7.4 volt pack. if they are wired in parelell that means that you add the compasity (MAH). they will get about 12 minutes on the track running WOT, but they will also drop about a pound off my truck, so that may result in more runtime.