Small device to ensure your RC model has enough power when playingLow voltage alarm buzzer for 7.2v-14.4v lipo batteryQuick test for your lipo before flightUsed as inflight alarm if you are not sure the maximum flight timeSmall device to check the battery voltage to avoid permanent damageHow To Use:When testing full power(>3.6V) 2S(7.2V) lipo battery - 2 green led keeping lightWhen testing full power(>3.6V) 3S(10.8V) lipo battery - 3 green led keeping lightWhen testing full power(>3.6V) 4S(14.4V) lipo battery - 4 green led keeping lightWhen voltage Includes 2x Low Voltage Bazzer