The Capri Tools Brake Lining Thickness Gauge lets you easily identify the thickness of your brake lining and determine whether the lining needs to be replaced. Simply place the brake lining next to each gauge, and the color coded system quickly tells you whether the brake lining is lightly worn (green), moderately worn (yellow) or needs replacement (red). 8 gauges: 3 green, 3 yellow, and 2 red. The gauges are entirely made of steel – durable and long lasting. Metric/SAE markings are included on all gauges: 3 green (12, 10, 8 mm or 0.4724, 0.3937, 0.3150 in.), 3 yellow (6, 5, 4 mm or 0.2362, 0.1969, 0.1575 in.), and 2 red (3, 2 mm or 0.1181 or 0787 in.).