OTC's Brake Pad Gauge allows for a definitive measurement of brake pads to determine remaining lifeUnique design allows for measurement on the vehicle without the removal of any components in most cases (wheel assembly or brake caliper)Quick, easy verification of brake pad condition via color code scale - Red means No, Green means GoCrafted from rugged materials to ensure long term performance and durabilityTo calibrate: when probe tip is in locked position (resting on either body ledge), barrel measurement should be 4mm - adjust set screw and end screw as necessary to achieve 4mm measurementThe brake pad gauge allows for a definitive measurement of brake pads to determine remaining life. Unique design allows for measurement on the vehicle without the removal of any components in most cases (wheel assembly or brake caliper). Quick reference of brake pad condition via color code scale and attain measurement without removing any parts from the vehicle.