The Centipede is the metric "ruler in the round". It is a functional keychain accessory that you'll use more times than you ever thought. The Centipede is a rod of 4.76 mm [3/16"] diameter 6Al-4V grade titanium with grooves cut at 2 mm increments up to 8 cm long. The outside surface is bead blasted to a uniform matte finish and new grooves are then cut every centimeter for ease of reading. Use it to check your tire tread depth, check the width of your broken fan belt, measure metric screw lengths, or calculate distance on a map.