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 Commodity Code Description 90 17 20 00 Other drawing, marking out or mathematical calculating instruments