Centipede Titanium Metric Ruler keychain accessory from TEC Accessories. This nifty measuring tool features cut grooves every 2 mm up to 8cm long, with larger cuts every 1 cm. The possibilities are endless...check your tire tread depth, check metric screw sizes, measure a broken fan belt or hose, check blade lengths etc. Made from 3/16" diameter solid 6AL-4V titanium. Check out the Inchworm model for imperial measurement. Includes an 8.6mm diameter split ring for attachment.