Portable and compact design: built to be carried on a keychain, this Keychain Alcohol Tester measures approximately 7 x 5 x 2 cm for convenient everyday use. LED indicators: three distinct LED lights provide a visual readout of your blood alcohol content. Color cues are Green for safe, Yellow for caution, and Red for danger. How to use: press and hold the button to warm up, then blow into the inhaler for 5 seconds to obtain quick and reliable results. The design is simple and accessible for users of all experience levels. Battery operated: powered by two AAA batteries (not included), this device allows for over 80 tests per battery installation. Practical use scenarios: Before driving after a social event or night out to assess your fitness to operate a vehicle. At home or in the workplace before using heavy equipment or returning to duties that require alertness. While traveling or on the go, keeping it on your keychain for easy, ondemand checks.