The HTS does not specify a precise thickness cutoff between foil and sheet within heading 790500 — both are classified under 7905000000. However, trade practice generally treats material below approximately 0.15 mm as foil. When thickness is near any borderline, documenting the nominal thickness and the supplier's product designation on the commercial invoice helps support the classification.

Continental European producers have invested heavily in continuous casting and rolling technology optimized for architectural-grade zinc alloys (typically zinc-copper-titanium), and European building standards have driven decades of product development in this segment. US demand for high-specification architectural zinc cladding and roofing largely relies on these established European mills because comparable domestic production capacity is limited.