The OEM 8 Piece Manual Brake Gauge Set is used to measure brake lining wear. Color coded brake gauge measures remaining brake lining. Constructed of 20 gauge sheet metal with durable powdercoat finish. Includes Sizes: Red: 2, 3mm, Yellow: 4, 5, 6mm, Green: 8, 10, 12mm. Red indicates must be serviced, Yellow indicates should be serviced, Green indicates no service needed. Designed for professional auto mechanics and heavy duty applications.