Tread depth meter. Useful when you need to accurately determine the remaining tread depth of a car tire. For example, you are selling or buying a tire that has been driven and you want to be sure that the tread depth is acceptable for further use of the tire. The tread depth gauge is like a small writing pen. You insert one end into the tread and on the back side you get a reading on the measuring scale. The material of construction is stainless steel and ABS plastic.