Believe it or not, my wife wanted one of these to measure tumors and other foreign bodies in animals (she's a vet, not a serial killer). Being a tool fanatic, she instructed me to find her without breaking my back. If you know anything about calipers, you know that when you need lab or industrial measurements for extremely precise work, they can be very, very expensive. We are not. I did a little research and they were popular for consistent metrics and good construction. You want the measuring side of the device to be flat and level so you get the same readings when using the outer and inner measuring faces. From my home testing, this is exactly the case with these calipers, with a deviation of no more than 0.02mm. This is definitely sufficient for our needs. Look, you know, if you want insane accuracy, and if you do, then you don't have to look at a caliper that costs less than $100. But for the amateur, general contractor, or novice engineer, they will come in handy. So why only four stars? The buttons on the device are cheap rubber buttons that can stick and get stuck if you press them at an angle. Not a big deal and it's easy to fix but still annoying. Otherwise there are no complaints. If you have any questions, please feel free to leave a comment. For your health!