GearWrench 3962 Brake Lining Thickness Gauge Color Coded Brake Gauge Identifies Thickness Levels for Brake Lining Inspection Metric - 8, 10, & 12mm (Green), 4, 5, 6mm (Yellow), 2 & 3mm (Red) SAE - 0.3150 to 0.4720" (Green), 0.1575 to 0.2382" (Yellow), 0.0787 to 0.1181" (Red)