Explanatory notes
… any instruments, apparatus, etc., falling in headings 90.01 to 90.12 or 90.15 to 90.30; in particular, the … excluded : (a) Astronomical instruments of heading 90.05 . (b) Microscopes ( heading 90.11 or 90.12 ). (c) … But the heading excludes standard optical flats ( heading 90.01 ), and interferometers for measuring refractive …