The RPM Ride Height Gauges 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 on the inch scale (#81300) represents 0.025” and on the metric scale (#81150), 0.5mm. (for extreme accuracy, the graduations are far enough apart that they may be split to read as little as 0.012” [#81300] or 0.25mm. [#81150])! Included with the gauge is a spring-loaded tensioning knob to keep the gauge positioned while checking & setting positions on the gauge. The RPM #81300 Ride Height Gauge (inch scale) has a range from 0.150” to 1.150” and the #81150 Ride Height Gauge (metric scale) has a range from 4mm. to 29.5mm.! Nothing is more accurate than an RPM Ride Height Gauge!