9002.20 - Filters and parts and accessories thereof:

This HTS category, 9002.20, specifically covers filters and their associated parts and accessories. These filters are designed for use with optical instruments and apparatus, falling within the broader scope of Chapter 90 which deals with precision instruments and apparatus. The key characteristic is their function as a filter within an optical system, modifying light in a specific way, such as absorbing certain wavelengths or reducing intensity.

Within the context of HTS code 9002, which addresses assembled optical elements and their parts, this subcategory distinguishes itself from siblings like "Objective lenses and parts and accessories thereof" (9002.10) by focusing solely on the filtering function rather than light gathering or image formation. While objective lenses aim to focus light, filters within this classification are intended to manipulate the light that has already passed through or will pass through an optical element.

The subcategories of 9002.20, namely 9002.20.40 (Photographic) and 9002.20.80 (Other), reflect the primary application or purpose of these filters. "Photographic" filters are those specifically designed for use in photographic equipment, while the "Other" category encompasses filters for a wide range of optical instruments and apparatus not specifically photographic in nature. This subdivision allows for a more granular classification based on the end-use of the filter.