Explanatory notes
… crystal 7013.42 - - Of glass having a linear coefficient of expansion not exceeding 5 x 10 -6 per Kelvin within a … glass, lead crystal, glass having a low coefficient of expansion (e.g., borosilicate glass) or of glass ceramics … consisting of a simple mirror are, however, excluded (see Explanatory Note to heading 70.09 ). On the other hand, this …