Hitec RCD 44210 Battery Buzzer Low Battery Voltage Alarm High Pitch Warning Sound, Input Voltage: 7.4 ~ 16.8 volts Battery Type: 2 ~ 4S LiPo, LED Status Indicator Voltage Select: 3.2V/3.3V/3.4V/3.5V 0.05V, Net Weight: 11g, Dimension: 1.97 x 1.10 x .49 in.