These hex nuts are internally threaded and have a hex drive for nearly all general applications. The most commonly used nut, hex nuts are used in any application with a mating male threaded machine bolt or screw. Can be used with any fastener with a machine screw thread. Hex nuts are used with bolts and washers of the same diameter, material, and finish. The package size designates the inner diameter and the number of threads per inch or thread pitch.