This is the real deal. This isn't a $9.99 key chain tester. This is the same kind that the police use.
I bought it to gauge myself as I drank to see where I was at. I used it a lot at first under various conditions. For example, on empty stomach versus full. After first drink, after second drink and so on. Then gathered the data every 5 minutes or so to build a data table as the number raised and then went down.
Was very useful for gathering data. Having collected the data, I hardly use it anymore.