22749 - 067000002 - This is the Low Voltage Buzzer for 2S/3S Li-Po Battery. For: 2S/3S Li-Po Battery. Specification: Measure 2S/3S Li-Po battery - Prevent the Li-Po battery damaged from low voltage - Buzz with red LED if Li-Po cell drops below 3.3V - Reverse polarity protection - Useful for Air-RC while the LED cannot be seen - Compact in size: can be put in micro-heli or other models - Light weight (5g) - Dimensions: L38.0 x W20 x H10 (mm).