Note:The product does not Inculde batteries[Product function]1. Digital display of alcohol concentration results with prompt tone2. Quick response and recovery3. Alarm points can be selected4. Red backlight5. Automatic shutdown and power saving function6. The mouthpiece can be replaced7. The digital alcohol breath tester has a key chain, which is very convenient to carry.Battery: 2'AAA' alkaline batteries (NOT INCLUDE)Sensor: advanced semiconductor oxide alcohol sensorRange: 0.00-0.19%BAC & 0.0-1.9g/l (or 0.00-0.95mg/l BRAC)Accuracy: 0.01% BAC(0.1g/l)A breathalyzer or breathalyser (a portmanteau of breath and analyzer/analyser) is a device for estimating blood alcohol content (BAC) from a breath sample. The breathalyzer is one of the most affordable breathalyzers available. It can be used in a wide variety of settings including clinical test applications and for personal use. Its uses advanced semiconductor alcohol sensing technology to quickly take a breath sample and provide a blood alcohol content (BAC) estimate. The lcd graphic display will indicate how inebriated you are, whether it be dangerous (over 0.05% bac), unsafe (approx. 0.02% bac) or safe (under 0.02% bac). Displays 'caution' when result is within 0.02% - 0.05%, displays 'danger' when result equals to or higher than 0.05%.