The Combined Nomenclature (CN), v1:2018
9002 20: Filters, optical, being parts of or fittings for instruments, apparatus and appliances, framed or mounted
https://www.dst.dk/en/Statistik/dokumentation/nomenklaturer/kn?id=97dd4f6e-1b47-43b5-8532-380d3d1b7c2f