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 16 Nuts of iron or steel Commodity Code Description 73 18 16 00 Nuts of iron or steel 73 18 16 10 For bolts having a shank of an external diameter not exceeding 16 mm 73 18 16 90 Other