I have always used the "coin technique" when measuring tread depth. I would always have to look up to figure out which coin and what part of the coin to use for my various depths (summer vs. snow tires). This is inexpensive and so much easier!

I've only recently decided to pay more attention to my tires (since moving to Chicago) and this is a good addition to my tool collection. It works just like you'd expect it would - press the small screwdriver-looking pointer in between the treads in the middle of your tire and then pull it out and read the depth measurement (it stays in position until you push the measuring stick down again). The numbers on the measurement stick are printed in a spiral all the way down the stick, presumably because it's too small to fit all the measurements on one side. It had a little oil at first but now I don't notice any.

I was looking for an easy way to measure tread wear on a new set of tires. This is a cheap and easy way to do so. It was quite oily when I took it out of the package. Not sure if that is so it slides easily or to prevent rust. It is all metal so possibly for both. Overall I'm happy with it and would recommend it.

This gauge is very easy to use, and provides quick determination of tread depth for each tire. One does not need anything more expensive than this item for its intended purpose.

Oily, but it's cheap and it works. Because of the oil on the shaft, I store it with the shaft completely compressed.