This is the best tool for setting the depth/height of a router and saw with reasonable accuracy. It's not perfect (see below), but it's still far more accurate than setting up the machine ruler, and so inexpensive there's no reason not to use it. It is read in metric/inch decimals or inches. It should be noted that the case is plastic and will therefore flex somewhat depending on how you hold it on your work surface. Holding it at the top of the finger grip I get quite a bit of flex, about +/- 5 thousandths. I've had the most luck, just pressing two fingers on the bottom of the grip reduces the flex to about +/- 1 thousandth. To be honest, for woodworking adjusting the depth of cut is fine, a few thousandths just isn't a problem. If I were to use this for metalworking it might not be acceptable. All in all, this is a great piece for the price.