A tapered gauge gets its accuracy by effectively stretching any scale for accurate reading. These stretch the standard scale by a factor of seven. When a thickness difference of 3mm is stretched over 22mm of the scale, small differences in thickness can easily be measured with fine accuracy. The aluminum gauge can be used many ways: for setting fences, router bits and drill-press stops, as well as making any gap easy to measure and, therefore, easy to fill, if you happen to be repairing work.Each one is hard anodized, a process that makes the surface as hard to scratch as tool steel, yet leaves it easy to write on with a pencil. In most uses accurate to ±0.05mm, they are guaranteed to have no greater error than 0.125mm in any measurement. Simple, effective tools in the scale of your choice - fractional in 1/64" graduations, decimal in 0.010" graduations, and metric in 0.2mm graduations. All have fine tips (0.8mm thick) and measure up to 28mm (or equivalent) thickness. Each comes supplied in a case.