The ultra-thin design allows the tool to position the back of the brake pad backing plate, allowing the probe to measure the distance between the underside of the backing plate and the brake disc. The ingenious time-saving tool is a necessary tool for any garage. Measure the brake pads on the vehicle without removing the wheels. Note: The data are all measured manually, please allow 1-3cm error due to differences in light and display, there may be some color differences, please refer to the actual item received.