Usage Tips: This product does not contain batteries Product overview: digital display of alcohol concentration results, prompt tone; rapid response and recovery; optional alarm point; red backlight; automatic shutdown and energy saving function; replaceable mouthpiece with 5 mouthpieces Product size: 118*70*28mm Open the back cover of the detector and install 2 AAA alkaline batteries. Using high sensitivity semiconductors, the data is accurate and fast. LED backlight digital display, more convenient to observe at night EASY TO USE AND PORTABLE: Simple to use, easy to carry, compact and delicate in appearance, save space for you, can be put in your pocket or bag when gathering with friends, and take it with you when you travel safely. Sensitive buttons that can be turned on and off with a single press. After 10 seconds of display, the BAC will automatically turn off. In order to get more accurate test results, users are recommended to repeat the test 2-3 times. Note: When the tester is first taken out of the package times or if the tester is not used for a long time, the sensor surface will be oxidized and the user should preheat the product for several times before performing the alcohol test.< /p> The nozzle is healthy and environmentally friendly, safe and non-toxic; streamlined handle design, beautiful streamlined design, beautiful hand feeling