Division 4 For the purposes of heading 7019, the expression ‘glass wool’ means:

1. (a)

   mineral wools with a silica (SiO₂) content not less than 60 % by weight;

2. (b)

   mineral wools with a silica (SiO₂) content less than 60 % but with an alkaline oxide (K₂O or Na₂O) content exceeding 5 % by weight or a boric oxide (B₂O₃) content exceeding 2 % by weight.

Mineral wools which do not comply with the above specifications fall in heading 6806.