4Pcs 2 in 1 LiPo Battery Voltage Tester RC Low Voltage Buzzer Alarm for 1-8S …
1-8S LiPo / Li-ion / Li-Mn / Li-Fe battery. The black button between the two speakers is the setting key. Alarm Set Value Range: OFF – 2.7V – 3.8V. Super loud alarm that sound makes it easier to find your drone.