Aluminum tube or pipe fittings (for example, couplings, elbows, sleeves).

&&Section 10 of the Customs Tariff directs that classification of imported goods shall be determined in accordance with the General Rules for the Interpretation of the Harmonized System. Section 11 of the Customs Tariff states that in interpreting the headings and subheadings, regard shall be had to the World Customs Organization's (WCO) Explanatory Notes to the Harmonized Commodity...

Source: advance_ruling (C-2018-001205)