For outer diameters in the 215.9–406.4 mm range, the US schedule creates separate 10-digit lines based on whether wall thickness is below or at/above 12.7 mm (e.g., 7304191060 for alloy non-stainless pipe with OD 215.9–406.4 mm and wall ≥12.7 mm). This split reflects historical antidumping scope language, so misreporting wall thickness can place a shipment in the wrong line and either expose it to — or incorrectly exempt it from — a trade-remedy order.

The dividing line is steel type: pipe meeting the chemical composition definition of stainless steel (generally ≥10.5% chromium by mass with low carbon) classifies under 730411, while all other seamless iron or steel line pipe — including carbon, low-alloy, and high-strength alloy grades — falls under 730419. The mill test certificate is the primary document for making this determination at entry.