Natural rubber, EPDM, neoprene (polychloroprene), nitrile (NBR), and SBR are all common compound bases for noncellular sheet. Under the SITC heading they are grouped together, but the corresponding HTS tariff schedule may subdivide by rubber type or by whether the rubber is natural or synthetic, so the compound chemistry should be confirmed for precise HTS classification.

Further fabrication — such as cutting to a specific gasket shape, bonding to a metal backing, or adding a pressure-sensitive adhesive layer — can move the product from a rubber sheet heading into a finished rubber article or composite heading. Importers should assess whether the product arrives as stock material or as a ready-to-install component, as the distinction affects both classification and duty rate.