Low Voltage Buzzer Indicator 2-4s LiPo Alarm - TURBINES RC
Amazon.com: RC Battery Low Voltage Alarm,Simulation 2-4S Battery Low Voltage Alarm Fit for SCX10/TRX4 1/8 1/10 RC Car Model Accessory (Black) : Electronics
2-4S Low Voltage Buzzer Alarm Lipo Battery Voltage Indicator Tester for RC Car | eBay