The Faithfull High Speed Steel Rosehead Chubby 90 included angle Countersink is used for countersinking screw holes for flush fitting of screw heads in mild steel, plastics and non-ferrous metals. They are also suitable for working on wood, plywood, MDF, and other man-made boards. They can be used in both hand tools, and power drills. Specifications Type Rosehead - Chubby. Size 13mm (1/2in). Shank Diameter 6mm (1/4in).