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 18 APPARATUS AND SIGHT-TESTING INSTRUMENTS. 90 18 41 DENTAL DRILL ENGINES, WHETHER OR NOT COMBINED ON A SINGLE BASE WITH OTHER Commodity Code Description 90 18 41 00 DENTAL DRILL ENGINES, WHETHER OR NOT COMBINED ON A SINGLE BASE WITH OTHER