7304.29.31 - Threaded or coupled

This HTS category, 7304.29.31, specifically covers seamless casing made of iron or steel that is of a kind used in drilling for oil or gas. The distinguishing feature of this subcategory is that these casing pipes are threaded or coupled, indicating a connection mechanism for assembly in wellbore construction. This contrasts with sibling category 7304.29.41, which would cover similar casing but without these specific threaded or coupled features.

Within this classification, further distinctions are made based on the outside diameter of the casing. The subcategories highlight that the diameter is a critical factor for the intended application and structural integrity in oil and gas extraction. These subdivisions allow for precise classification based on the physical dimensions of the casing, ranging from those with smaller outside diameters to those exceeding 406.4 mm.

The existence of these subcategories based on diameter reflects the varied requirements and operational conditions encountered in drilling operations. Different diameters are suited for specific well depths, pressures, and geological formations, necessitating granular classification to ensure accurate import/export duties and regulatory compliance.