Never again have a doubt about how much alcohol you have had to drink or whether you or your friend is legally OK to drive. This mini breathalyzer has a traffic light readout style system making it super easy use. Simply blow for 5 seconds then wait. A green indicating light and you are good to go; yellow and you may want to wait a while before you go home; while red indicates you should hand your keys to a friend. This is great reference tool for seeing if you have had just a little too much to drink.