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 26 Instruments/apparatus for measuring the flow... of liquid or gases, nes 90 26 20 For measuring or checking pressures Commodity Code Description 90 26 20 00 For measuring or checking pressures