This is a new product combining all the voltage measurements with low-voltage alarm function. Li-Po Battery Voltage Buzzer+Indicator: directly plug it into your operating battery, it will monitor the conditions of your battery all the time, so your entertainment will be more interesting and limitless. Features: * With a push key by which you can change the value settings and save. * When voltage is below the set value, it will buzzer very loudly with red LED light. (pre-set value is 3.3V) * Mini shape, no larger than a common key. * Compact, easy to carry. * Really useful in flight if you can`t see the lights. * Use for 1-8s Lipo/Li-ion/LiMn/Li-Fe. * Voltage detection precision: ±0.01V * 1S test mode voltage range: 4-15V * Low voltage alarm mode for 2-8S * Alarm set value range: Off 2.7-3.8V * Package weight: 9g