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, PHOTOGRAGHIC, CINEMATOGRAPHIC, MEASURING, CHECKING, PRECISION, MEDICAL OR SURGICAL INSTRUMENTS AND APPARATUS; CLOCKS AND WATCHES; MUSICAL INSTRUMENTS; PARTS AND ACCESSORIES THEREOF 90 01 NOT OPTICALLY WORKED. 90 01 90 OTHER PRISMS, MIRRORS & OTH. OPTICAL ELEMENTS, OF ANY MAT., UNMOUNTED... 90 01 90 90 OTHER PRISMS, MIRRORS & OTH. OPTICAL ELEMENTS, OF ANY MAT., UNMOUNTED... Commodity Code Description 90 01 90 90 000 OTHER PRISMS, MIRRORS & OTH. OPTICAL ELEMENTS, OF ANY MAT., UNMOUNTED...