Overall Length - 5 1/8", Shank Diameter - 1/2" x 3 7/8", Pilot Hole Diameter - 3/16". Used in spot facing and counterboring operations. . These counterbores can be used with a wide variety of pilots. The shank diameter of the pilots ordered must be the same as the pilot hole size in the counterbore. We stock a complete range of pilots; please inquire.