Base-metal conduit tubing lined with insulating material classifies under 854790 in this heading, not with insulated wire or cable. The key is that the article is a conduit — a protective tube for routing conductors — with an insulating lining, rather than a conductor itself. Unlined metal conduit classifies in the base-metals chapters.

A fitting under 854720 must be primarily of insulating material and designed to insulate, support, or separate conductors within an electrical machine or apparatus. A plastic housing or enclosure that serves a structural or protective purpose rather than an insulating one is more likely a part of the specific apparatus it belongs to, classifying with that apparatus. When the insulating function is incidental to the part's structural role, classification follows the apparatus.