This Is Harry"s Old Fashion Wing Bolt Drilling Guide from Harry B Higley. FEATURES: Solid steel construction Holes provided for ¼" and #10 wing bolts Easily drill perfect holes for the bolts used to hold the wings to the fuselage of a plane. INCLUDES: One Drilling Guide SPECS: Diameter: ½" (13mm) Thickness: ¾" (19mm)Harry HigleyPart HIGWBG001