Common Parts : Airy-Acc-LE-0026
It will warn you when it is time to land your helicopter
It will Buzz with very loud BB noise when any of the cells of your battery is under 3.3V, the volume is loud enough to alert you to land your helicopter immediately to avoid accident.

• The Alarm sounds and red lights to warn you, when the battery voltage is too low.
• It can prevent your Li-Po battery damaged due to low voltage.
• Good for 2 Cells 7.4V and 3 Cells 11.1V Li-Po Batteries.
  

• Small device to ensure your RC model has enough power when playing
  
• Low voltage alarm buzzer for 7.2v-14.4v lipo battery
  
• Quick test for your lipo before flight
  
• Used as inflight alarm if you are not sure the maximum flight time
  
• Small device to check the battery voltage to avoid permanent damage

• When testing full power (>3.6v) 2s (7.2v) Li-Po battery 2 green LED keeping light
  
• When testing full power (>3.6v) 3s (10.8v) Li-Po battery 3 green LED keeping light
  
• When testing full power (>3.6v) 4s (14.4v) Li-Po battery 4 green LED keeping light
  
• When voltage <3.3v, it will buzzer with red LED light
  
• Really useful in flight if you cannot see the lights

• 1 x Li-Polymer Battery Low Voltage Buzzer / Alarmer 2-4S (Double Speaker / 7.4V - 14.4V)

** color of this device might be different (green or red electronic board) sometime but it is the same.