Standard International Trade Classification
U.S. imports of Insulating Fittings for Electrical Machines — Other Materials (NES) (SITC 77329) totaled $21.6M in August 2026, imported from 39 countries.
Importers of Insulating Fittings for Electrical Machines — Other Materials (NES) paid $4.1M in duties in August 2026, an average duty rate of 20.47% — duty actually collected as a share of the imports that cleared customs, not the published tariff schedule. Insulating Fittings for Electrical Machines — Other Materials (NES) imports of $21.6M in August 2026 ran 14% above the year-to-date monthly average of $19.0M.
Last updated: August 2026 dataResidual insulating fittings made from materials other than ceramics or plastics — including mica composites, vulcanized fiber, epoxy-glass laminates (such as FR4 or G10), and similar engineered dielectrics — serve specialized roles in high-temperature motor windings, transformer coil supports, and precision switchgear where neither standard ceramics nor commodity plastics meet the thermal or mechanical requirements. The 'not elsewhere specified' scope of this heading means correct classification requires ruling out the ceramic (77326) and plastic (77328) headings first. Epoxy-glass laminates in particular are a widely traded subcategory used extensively in printed circuit board and power electronics manufacturing.
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1.8K import shipments a month
Common materials include mica-based composites (micanite, mica paper laminates), vulcanized fiber, epoxy-glass laminates (FR4, G10, G11), and fish paper. These materials are chosen for applications requiring high dielectric strength at elevated temperatures — such as slot liners in electric motors, coil end-turn supports in transformers, or arc barriers in switchgear — where plastics would soften and ceramics would be too brittle or heavy.
Importers should retain material composition certificates or technical datasheets confirming that the fitting's primary insulating material is neither ceramic nor plastic. For epoxy-glass laminates, a laminate grade designation (e.g., NEMA FR4, G10) and resin content specification serve this purpose. For mica composites, the mica content percentage and binder type should be documented. CBP may request this documentation during a tariff classification review.
Basic heading 332 of 642 in section 7
Basic heading 77329 · $21.6M of $172.0B
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Imports · August 2026
origin
Mexico and Canada together supply 51% of it. China pays 48.1% duty; Canada 4.6%.
customs district
Census does not publish district detail for this classification system.
destination
Census does not publish state detail for this classification system.
entry
Census does not publish port detail for this classification system.
ImportsExports
Imports
$21.6MYoY · free account
Exports
$18.0MYoY · free account
12-mo low · imports
Low · free accountOver the twelve months to August 2026, the U.S. imported $211.0M of Insulating Fittings for Electrical Machines — Other Materials (NES).
Through August 2026 · exports 10 of 12 months reported. Source: U.S. Census Bureau.