Square and rectangular HSS fall under 730661, while other non-circular cross-section profiles go to 730669. Circular HSS in carbon or nonalloy steel classify under 730630. The key is cross-sectional shape; all are welded closed profiles not dedicated to oil-field use.

Yes, they are independent measures and can stack. Section 232 tariffs apply on a country-of-origin basis across most iron and steel tubular products, while antidumping and countervailing duty orders attach to specific product scopes and specific countries. An importer may owe both on the same shipment; the applicable cash deposit rates should be confirmed at the time of entry.