The RPM Ride Height Gauge take the guesswork out of proper ride height adjustments! These gauges have a graduated scale along the upper edge of the base with easy to read lines and numbers. Each graduation represents 0.5mm. (for extreme accuracy, the graduations are far enough apart that they may be split to read as little as 0.25mm.)! Included with the gauge is a spring-loaded tensioning knob to keep the gauge positioned while checking & setting positions on the gauge. The RPM Ride Height Gauge has a range from 4mm. to 29.5mm.! Nothing is more accurate than an RPM Ride Height Gauge!