Counterbores with built-in pilots (sometimes called solid pilot counterbores) are made from one piece of metal, which means the pilot cannot be removed. They can be used with one size of hole to create a flat-bottomed cavity at the top of the hole so that a bolt, nut, or other part is hidden beneath or sits flush with the top of the hole when installed into it. The pilot keeps the counterbore centered in the hole to ensure a level seat. These sets contain multiple solid pilot counterbores in a range of sizes.