HS Code 731816: Steel Nuts in Real U.S. Import Trade
Behind the six-digit chapter lies a surprisingly specific category — and several of the largest U.S. manufacturers are filing under it every month.
What Does HS Code 731816 Actually Cover?
Under the Harmonized System, HS Code 731816 falls within Heading 7318, which covers threaded articles of iron or steel. The six-digit code 731816 is reserved specifically for nuts — the internally threaded fasteners designed to mate with bolts, screws, or studs. In practice, this includes hex nuts, flange nuts, lock nuts, and other steel nuts that have internal threads.
It excludes nuts made of other materials, non-threaded fasteners, or complete fastener assemblies that may be classified elsewhere under the same heading. The U.S. HTSUS subheadings add further country-specific detail, but the six-digit core remains the universal language for trade statistics and tariff comparison.
Yet a precise legal definition alone does not tell importers what they actually need to know: how do successful companies describe this product when they file their entry summaries?
Real Import Filings from Industry Giants Under 731816
According to TradeMagellan’s exclusive analysis of U.S. customs data, several major manufacturers repeatedly use HS code 731816 for identical commodity descriptions. The records show that these filers do not treat “nuts” as a vague catch-all term. Instead, they carefully align their product descriptors with the commercial reality of the part.
TradeMagellan U.S. import records show the following key players filing under HS Code 731816:
| Importer of Record | Product Description as Filed |
|---|---|
| STELFAST INC. | NUT |
| HMMA LLC. | NUT, FLANGE |
| MOBIS ALABAMA LLC. | NUT;HEX,FLANGE |
| FUJI COMPONENT PARTS USA INC. | NUT |
| ITAC ALABAMA LLC. | NUT;HEX,FLANGE |
Take note of the variation. HMMA LLC and ITAC ALABAMA LLC — both deeply embedded in the U.S. automotive manufacturing supply chain — describe their products as flange nuts or hex flange nuts. MOBIS ALABAMA LLC, a major auto parts supplier, files the combined descriptor NUT;HEX,FLANGE, which tells the customs examiner the exact geometry and application in one line.
On the other hand, STELFAST INC. and FUJI COMPONENT PARTS USA INC. routinely use the single word NUT. Even with this simpler language, they still land on 731816. This demonstrates that HS code assignment is driven by the physical characteristics of the component — not solely by the marketing name or brand terminology.
Why Matching the Descriptor to the Code Reduces Classification Risk
Misclassification is one of the most common — and most costly — errors in customs compliance. A shipment of steel nuts entered under the wrong six-digit code can trigger duty underpayment or overpayment, hold cargo at import, and produce audit exposure for years.
Learn from Filers That Handle High-Volume Fastener Imports
The companies listed above are not occasional importers. They operate major manufacturing and assembly facilities in the United States, and their customs brokers maintain highly disciplined product classification routines. By reviewing their public filing patterns, other importers can check whether their own product descriptions align with what leading competitors are already declaring.
- Be specific when the part is specific. If your product is a flange nut, filing “NUT, FLANGE” is more defensible than simply “NUT.”
- Use the correct material basis. HS 731816 applies only to iron or steel nuts. If your nut is made of aluminum or plastic, the classification should shift elsewhere.
- Include harmonization details downstream depending on add-on features. For example, nylon-insert lock nuts may have their own statistical suffixes in the U.S. — but the six-digit core remains 731816.
- Let commercial documents match customs declarations. Invoices, packing lists, and entry summaries should tell the same story to avoid red flags during document review.
The hidden value of analyzing TradeMagellan’s importer database is not just seeing which code is popular — it is understanding how real operators word their descriptions in the CBP environment. Classifiers who compare their own draft declaration against the filings of STELFAST, HMMA, MOBIS ALABAMA, FUJI COMPONENT PARTS, and ITAC ALABAMA can catch vague descriptions before they turn into costly errors.
Follow the Data, Not the Guesswork
Legal texts tell you what HS code 731816 should mean. TradeMagellan’s transaction-level data tells you what actual importers are doing at the border. For customs brokers, trade compliance managers, and freight forwarders, the second perspective is just as important as the first.
TradeMagellan’s data model aggregates bill-of-lading records and entry summaries to reveal the real-world language of trade. When you see an established player like MOBIS ALABAMA filing NUT;HEX,FLANGE under 731816, you are not looking at theory — you are looking at a compliance pattern refined over thousands of shipments.
