No need for other tools to set a baseline diameter—these bore gauges have a built-in micrometer head. Use them to check diameters and test for issues with roundness in engine cylinders and other parts. They have a two-point contact system, which is the most common design for bore gauges. For a long service life, the jeweled bearings in the dial head resist wear, and a plastic cover protects the head from scratches and drops. With hollow grips, these bore gauges are easy to hold and prevent heat from your hands from skewing accuracy.

To use them, set a baseline measurement with the micrometer head. As you move the gauge in the hole, the variation from the set measurement displays on the dial right away. Switch out the anvil to measure bores of different diameters.