Description: 【Wide Compatibility】: Compatible with 1S to 8S lithium batteries, this voltage display monitor automatically detects the voltage of each cell and the total battery voltage, ensuring accurate monitor for a variety of battery types 【Double Functionality】: Combines real time digital voltage display with a low voltage alarm system; when the voltage drops below your preset value, both a loud buzzer and a flashing red LED alert you immediately 【Easy To Operate】: Easily adjust the low voltage alarm threshold from the default 3.3V using a simple button press; your preferred setting is automatically saved for future use 【Premium Material】: Crafted from quality PC , this compact low voltage buzzer alarm (4 x 2.5 x 1.1 cm) is lightweight yet robust, making it ideal for on the go battery management 【Reverse Connection Protection】: Voltage checker features built in reverse polarity protection to both your batteries and the device during connection, providing peace of mind during everyday use Specification: Material: PC Size Chart: Product Dimensions: 4cmx2.5cmx1.1cm/1.57inchx0.98inchx0.43inch Package Includes: 3 Battery Voltage Testers Note: Please allow slightly errors 1-2cm/0.39-0.79inch differences due to manual measurement.