An IGU under heading 7008 consists of two or more panes held apart by a spacer and hermetically sealed at the edges, creating an insulating air or gas cavity. Laminated glass — layers bonded together with an interlayer — classifies under a different heading in the glass chapter. The sealed-cavity construction is the defining feature for 7008.

Yes. The US has issued antidumping and countervailing duty orders on certain insulating glass units from specific countries. Importers should check the current scope of any active orders with CBP or the International Trade Administration before shipment, as scope rulings can affect whether a particular product configuration is covered.