Overall Length - 4 1/16", Shank Diameter - 3/8" x 3 1/16", Pilot Hole Diameter - 5/32". 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.