While going through the PCL catalog, I saw this cheap little tire tread depth gauge that I thought would be a nice addition to my cabinets and the cabinets of others like me. It's small enough so that you can put it in your glove box or emergency kit or you can also take it to the track & monitor your tread depth from the start to the end of your session.
The gauge displays two different units of measurement:
inches (Decimal Point / Fractions)
0 - 25mm in 0.01mm increments
0 - 1" in 1/64" increments
SR44 Button Cell