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 31 Measuring or checking instruments, appliances and machines, not specified or included elsewhere in this Chapter; profile projectors. 90 31 10 Machines for balancing mechanical parts 90 31 10 00 Machines for balancing mechanical parts Commodity Code Description 90 31 10 00 000 Machines for balancing mechanical parts