Section 18 Optical, photographic, cinematographic, measuring, checking, precision, medical or surgical instruments and apparatus; clocks and watches; musical instruments; parts and accessories thereof 90 Optical, photographic, cinematographic, measuring, checking, precision, medical or surgical instruments and apparatus; parts and accessories thereof 90 17 Drawing, marking-out... instruments; instruments for measuring length... 90 17 20 Other drawing, marking out or mathematical calculating instruments 90 17 20 00 Other drawing, marking out or mathematical calculating instruments Commodity Code Description 90 17 20 00 000 Other drawing, marking out or mathematical calculating instruments