HSN Code 9001 refers to "Optical fibres and optical fibre bundles; optical fibre cables (excluding made up of individually sheathed fibres of heading 8544); sheets and plates of polarising material; lenses, incl. contact lenses, prisms, mirrors and other optical elements of any material, unmounted (excluding such elements of glass not optically worked)." This classification code is essential for identifying optical products for import/export purposes based on their nature, composition, and intended use. Common products under HSN Code 9001 include optical fibre cables, polarising sheets, contact lenses, optical lenses, and prisms. Additionally, the GST rate for optical fibres and related items under this code supports accurate trade compliance.