8307.90 - Of other base metal:

This HTS category, 8307.90, encompasses flexible tubing and pipes manufactured from base metals *other than* iron or steel. These items are typically used for conveying fluids or gases and can be supplied with or without attached fittings. The key distinguishing factor for this classification is the material composition of the tubing itself, specifically excluding ferrous metals.

In contrast to its sibling category, 8307.10, which specifically covers flexible tubing of iron or steel, this heading is for all other base metal constructions. This includes tubing made from, but not limited to, copper, aluminum, nickel, zinc, lead, or tin alloys. The purpose and construction (e.g., corrugated, braided) are secondary to the primary material of the tubing for the initial distinction at this level.

Within this category, further subdivisions are made to account for the presence or absence of fittings. Subcategory 8307.90.30.00 specifically classifies flexible tubing of other base metals that are equipped with fittings, such as couplings, connectors, or end pieces. Conversely, 8307.90.60.00 covers all other flexible tubing of base metals that are not supplied with any fittings. This distinction allows for more granular tariff application based on the completeness of the product as imported.