7304.29.31.50 - Having a wall thickness less than 12.7 mm

This HTS category, 7304.29.31.50, specifically classifies seamless tubes and pipes of iron or steel that are used for drilling for oil or gas, and fall under the designation of "casing" of "other alloy steel." Crucially, these items are further refined by their physical dimensions. This particular subcategory applies to casing that has been threaded or coupled and possesses an outside diameter that is greater than 285.8 mm but does not exceed 406.4 mm.

The defining characteristic that distinguishes this category from its sibling, 7304.29.31.60, is the wall thickness. While this classification is for casing with a wall thickness *less than* 12.7 mm, the sibling category applies to casing with a wall thickness of 12.7 mm *or more*. This distinction is a critical factor in determining the appropriate tariff heading, reflecting different manufacturing processes and intended applications based on wall strength.

As this is a leaf node within the HTS, there are no further subcategories. Therefore, classification under 7304.29.31.50 is final based on the criteria of being seamless alloy steel casing for oil and gas drilling, threaded or coupled, with an outside diameter between 285.8 mm and 406.4 mm, and a wall thickness under 12.7 mm. Importers must ensure all these specific physical attributes are met for accurate classification.