Section 15 Base metals and articles of base metal 73 Articles of iron or steel 73 18 Screws, bolts, nuts, coach-screws, screw books... of iron or steel 73 18 29 Having a shank of an external diameter not exceeding 16 mm 73 18 29 10 Having a shank of an external diameter not exceeding 16 mm Commodity Code Description 73 18 29 10 00 Having a shank of an external diameter not exceeding 16 mm