Thank you for viewing. This product is a HiTEC battery low voltage alarm buzzer. It can be used for cars, boats, airplanes, etc. I used one for testing, but the others are new and unused. *There is no packaging. Since it has been about 2-3 years since the last use, I will consider it as an untested product. ・Precisely detects voltage drop of 2-4 cell LiPo batteries ・Notifies voltage drop with a loud buzzer and LED ・Detection voltage can be freely set between 3.2-3.5V ・Optimal for preventing over-discharge ・Volume can be adjusted by how the protective seal is applied Please feel free to comment if you have any questions.