7004.90 - Other glass:

This HTS category, 7004.90, encompasses drawn or blown glass in sheet form that has not undergone further working beyond the creation of the sheet. It specifically includes glass sheets that may possess an absorbent, reflecting, or non-reflecting layer. The key characteristic is that any applied layer is for modifying the glass's properties without altering its fundamental sheet form through processes like cutting to shape, drilling, or tempering.

Distinguishing this category from its sibling, 7004.20, is crucial. While 7004.20 deals with glass colored throughout the mass (body tinted), opacified, flashed, or similarly treated glass sheets, category 7004.90 covers those sheets that are not inherently colored or opacified in that manner. The focus here is on sheets where the primary defining characteristic is the presence of a surface layer for specific optical or functional purposes, rather than inherent coloration or opacity of the glass itself.

Within this category, further subdivision exists to refine the classification of these "other" glass sheets. The subcategory 7004.90.50.00 specifically addresses sheets that are not further specified. This typically includes glass sheets that have an absorbent, reflecting, or non-reflecting layer, and are not otherwise worked, and are not in a particular defined rectangular shape. The presence of a specific non-rectangular shape or other implicit differentiating factors would likely lead to classification under this residual "other" designation.