Material Composition Rules: How Fiber, Metal, and Plastic Content Decide Your Code

Material composition can decide an HTS classification, but the deciding rule depends on the product. Textile blends can be classified by the fiber that predominates by weight, base-metal articles follow their own statutory weight rules, and plastic-textile products may first need to be placed in the correct chapter before any percentage threshold matters. Where no specific legal note applies, weight becomes only one factor in the broader essential-character analysis. That makes accurate composition data critical. 

Fiber percentages, alloy chemistry, component weights, coating details, and even the denominator used for a percentage can change the result. This guide explains how those rules work across textiles, metals, and plastics, what information a product master should hold, and how rounding, incomplete specifications, and laboratory results can affect classification and audit outcomes.

Where Composition Decides the Code

Material composition decides a tariff code at four separate points, and each point asks a different quantitative question. Treating them as one question is the root error behind composition disputes.

Sequence is not optional. A percentage can select a tariff line only after the product has cleared the scope and exclusions of the heading containing that line. Running the percentage first gives a plausible code that collapses the moment someone reads the chapter note.

One distinction underpins everything below: a quantitative special rule is not an essential-character assessment. For a qualifying textile blend, or an article of base metal containing several base metals, the schedule supplies the governing weight rule outright. For an ordinary plastic-and-metal composite with no note on point, weight is one input among several and GRI 3(b) decides.

The Chief Weight Test for Fiber Blends

Section XI Note 2(A) covers goods classifiable in Chapters 50 through 55, or in headings 5809 or 5902, that contain two or more textile materials. Those goods are classified as though composed wholly of the textile material predominating by weight over each other single textile material. Only where none predominates does the note fall back to the last heading in numerical order among those equally meriting consideration, as the Section XI legal notes set out.

How Chief Weight Works

Chief weight is a plurality rule, not a majority rule. In a fabric that is 40 percent polyester staple, 35 percent cotton, and 25 percent viscose rayon, polyester governs even though it is under half the total because it exceeds each other single fiber. An exact 50/50 split is the opposite case: nothing predominates, so the numerical-order tiebreaker applies.

How Materials Are Grouped

Note 2(B) changes how the weights are grouped before that comparison runs:

• Determine the chapter first, then the heading within it, disregarding materials not classified in that chapter.

• Treat Chapters 54 and 55 as a single chapter where both are involved along with another chapter.

• Treat different textile materials as one material where the chapter or heading refers to them together.

• For woven fabrics, treat metal thread as a textile material, with metalized yarn and gimped horsehair yarn handled as Note 2(B)(a) directs.

Grouping is what makes "the largest fiber wins" unsafe as a shortcut. In HQ 081308, CBP combined synthetic and artificial man-made fibers at the relevant stage. After man-made fibers prevailed over cotton, the artificial component governed within that grouping because it outweighed the synthetic one.

How the Rule Applies to Finished Articles

For finished articles, Subheading Note 2(A) extends the same mechanism to products of Chapters 56 through 63, while Subheading Note 2(B) narrows what gets counted. Consider only the part determining classification under GRI 3, disregard the ground fabric in a ground-plus-pile or loop product, and apply the special embroidery rules.

Whole-product percentages answer a different question from the one the tariff asks. In apparel, the invoice rules call for the entire-garment breakdown plus separate breakdowns for shell and lining, which is why clothing classification rarely resolves off one content label.

Near-Ties, Rounding, and Laboratory Risk

Risk concentrates at the dividing line. A claimed 49/51 blend is a claim sitting one production variance away from reversing the governing fiber. In ruling N287182, CBP warned that the slightest variation in a stated 49/51 blend could alter the classification, and that laboratory analysis at importation could lead to reclassification. HQ H043009 carried the same warning for a stated 50/50 tent fabric.

Caution: Do not record a supplier's rounded label figure as the classification fact. A label reading "50/50" may be a rounding of 49.6/50.4, and the rounding is the difference between two codes.

Consumer-label guidance permits limited rounding in specified labeling contexts. Section XI Note 2 states the tariff test without any general classification tolerance of that kind, and the tariff text is the one CBP applies at entry.

Base Metal Predominance Under Section XV Notes 5 to 7

Alloy Classification Under Note 5

Metals follow their own statutory rules. Section XV Note 5 governs alloys other than the ferroalloy and master-alloy definitions specific to Chapters 72 and 74. An alloy of base metals is classified as an alloy of the metal predominating by weight over each other metal, not over all other metals combined.

Where an alloy contains Section XV base metals plus elements from outside that section, it counts as a base-metal alloy only when the total weight of the Section XV base metals equals or exceeds the total weight of the other elements. The Section XV notes also include sintered metal-powder mixtures, heterogeneous intimate mixtures obtained by melting other than cermets, and intermetallic compounds within the term "alloys." Note 6 then extends a tariff reference to a base metal to the alloys Note 5 attributes to it.

Multi-Metal Articles Under Note 7

Note 7 works one level up, after the goods are already treated as articles of base metal. Unless a heading requires otherwise, an article containing two or more base metals is treated as an article of the base metal predominating by weight over each other base metal.

Three counting conventions apply first:

• Iron and steel, including different kinds of iron or steel, count as one metal.

• An alloy counts entirely as the metal to which Note 5 attributes it, not as its constituent elements.

• A cermet of heading 8113 counts as one base metal.

Ruling N340532 shows both stages in sequence on a composite keychain. GRI 3(b) came first and made the metal components decisive over the decorative PVC. Once the article was treated as metal, Note 7 selected iron over zinc by weight, landing it in heading 7326. Between two base metals in an article of that kind, principal weight decides, not a second essential-character analysis.

Chapter-level definitions still override commercial habit. CBP's aluminum guidance, quoting Chapter 76 Subheading Note 1, separates "aluminum, not alloyed" from "aluminum alloys" using specified impurity limits together with an overall one-percent condition. An alloy designation on a purchase order does not settle HTS treatment.

Plastics Against Textiles: Scope Before Percentage

The plastic-textile boundary is a scope question first and a percentage question second. Section XI Note 1(h) excludes woven, knitted or crocheted fabrics, felt, and nonwovens impregnated, coated, covered, or laminated with plastics, where they are goods of Chapter 39. Chapter 39 Note 2(p) excludes goods of Section XI in return. Neither exclusion asks about weight.

Chapter 59 Note 2 supplies the working boundary for heading 5903. The heading takes in qualifying coated textile fabrics regardless of weight per square meter and plastic type, but excludes:

• Coatings or impregnation not visible to the naked eye, ignoring any resulting change of color.

• Products that cannot be bent manually around a 7 mm cylinder at 15 to 30°C without fracturing.

• Textile completely embedded in plastic, or visibly coated or covered with plastic on both sides.

• Partial plastic coatings applied so as to create designs.

• Cellular-plastic plates, sheets, or strip where the textile merely reinforces the plastic.

• Textile products of heading 5811.

Chapter 59 Note 3 separately defines plastic-laminated textile fabric as one or more fabric layers assembled with one or more plastic sheets or films by a bonding process, whether or not the plastic is visible in cross-section. The apparent conflict with the naked-eye criterion resolves by reading Note 2's treatment of impregnation, coating, and covering separately from Note 3's definition of lamination, rather than treating "coated" and "laminated" as interchangeable.

Only after heading 5903 scope is established does plastic percentage do any work. The current schedule carries "over 60 percent by weight of plastics" lines for certain fabrics specified in Section XI Note 9, and "over 70 percent by weight of rubber or plastics" lines for other man-made-fiber fabrics. Those are not universal Chapter 59 thresholds. Coating also cannot be inferred from "waterproof" or "PU leather": the invoice rules for fabrics potentially falling in Chapters 39, 40, or 42 ask whether the fabric is coated or laminated on both sides, the exterior, or the interior.

When No Note Applies: Weight, Value, and Role in Use

No universal "more plastic than metal" rule exists for ordinary finished composites. Where no heading and no legal note resolves the product, GRI 3(b) asks which material or component gives the article its essential character, weighing nature, bulk, quantity, weight, value, and role in use, with no single percentage controlling. Function often outruns mass: plastic drain bodies carried essential character in HQ H251048 despite metal components.

Value deserves a precise statement, because practitioners sometimes expect a chief-value test mirroring chief weight. Value is a named GRI 3(b) factor and a data point CBP can demand, since Form 28 contemplates requests for component breakdowns by weight and for actual component cost. It is not a standalone attribution rule of the kind Note 2 or Note 7 supplies.

The Composition Fields a Product Master Has to Hold

Composition rules are only as good as the record behind them, and the most useful discipline is putting the denominator next to every percentage. Total article weight, total fiber weight, one component's weight, and alloy chemistry are different denominators. A number without one is not evidence.

A product master that can answer composition questions holds:

• Generic fiber names with unrounded percentages by weight, totaling 100 percent.

• Separate data for shell, lining, pile, ground, and embroidery where each is independently relevant.

• Yarn construction that changes grouping: filament versus staple, synthetic versus artificial, core-sheath, metalized.

• Alloy chemistry by element and weight, including nonmetallic elements, tied to the production heat or lot.

• Component-level weights for each base metal in the finished article, not one "metal content" figure.

• Coating detail: polymer, cellular or compact form, which faces, visibility, grams per square meter, percentage by weight.

• Test method, sample identity, lot, preparation, units, uncertainty, and treatment of nonfibrous material.

Catalogs rarely hold that today. Gaia's analysis of the product data submitted to its platform found that 90% of input data provided to classify products is not good enough to result in a high-confidence classification, and composition fields are a large part of the shortfall. Description IQ addresses that gap directly, reading incomplete descriptions and identifying what is missing before a code is assigned, which is the same discipline needed when classifying a full catalog rather than one SKU.

Five Ways Composition Data Fails an Audit

Each failure below has been observed in CBP rulings or is a direct consequence of the notes above, and each one is a control problem rather than a knowledge problem.

1. Rounding a decisive percentage: Recording "50/50" when the source data reads 49.6/50.4 destroys the only fact the rule turns on. Require unrounded results with measurement uncertainty.

2. Classifying from substrate fiber alone: Coating visibility, two-sided coverage, embedment, flexibility, and reinforcing function allocate material between Chapters 39 and 59 before any weight threshold applies. Obtain cross-section data, coating-side data, polymer identity, and coating weight.

3. Treating marketing copy as fact: "Stainless," "recycled poly," and "cotton rich" are commercial names, not elemental percentages, generic fiber identities, or coating constructions. Translate each term into a testable specification.

4. Using the wrong denominator: Comparing total metal against total plastic when Note 7 asks which base metal predominates over each other base metal, or reporting plastic as a percentage of the coating rather than of the whole fabric, produces a confidently wrong answer.

5. Jumping to essential character: Deciding that plastic "does the work" before reading the legal note, or running an essential-character contest between aluminum and steel in an article already governed by Note 7, inverts the order.

What a Laboratory Result Changes on an Open Entry

A CBP laboratory result does not merely correct a product description. Where it changes the composition fact the analysis depends on, it changes the classification and the duty treatment with it. CBP has stated that its issued laboratory report is an official document that cannot be disregarded, and that where submitted information conflicts, CBP uses its own breakdown. An accredited outside report is valuable for pre-entry verification and for building a rebuttal record, but it does not automatically displace that result.

The route back depends on where the entry sits:

1. Before liquidation, from CBP: CBP may notify an importer of an increased rate or value on Form 29 where the statutory conditions are met.

2. Before liquidation, from the importer: A Post Summary Correction corrects an accepted ACE entry summary, generally filed within 300 days of entry and at least 15 days before scheduled liquidation, whichever comes first.

3. After liquidation: CBP identifies protest as the available route, filed within 180 days of liquidation.

4. Across prior entries: The importer of record carries the reasonable-care duty under 19 U.S.C. § 1484. Where a new result shows earlier entries were materially wrong, assess the full correction and disclosure picture rather than assuming the next entry cures the last twenty.

Composition is the classification input most likely to be tested by instrument and least likely to be documented to that standard. The same record that survives a laboratory challenge is what makes accurate HS codes reproducible across a catalog instead of defensible one SKU at a time.

Gaia’s Classification brings product details, material composition, and classification rules into one workflow. Teams can start a free trial to see how it works with their own products.

FAQs

Can a supplier declaration alone prove composition?

A supplier declaration supports the record but is not conclusive on its own. Where composition affects classification, it should be backed by controlled product data such as a bill of materials, mill documentation, or testing tied to the specific product.

Does an outside lab report override CBP's result?

No. An outside laboratory report does not automatically override a CBP laboratory result. In ruling H312071, CBP stated that its own laboratory report cannot be disregarded. Independent testing can still support the record when it covers the same SKU, lot, and composition question.

How is measurement uncertainty handled near a threshold?

No generally applicable CBP rule prescribing how uncertainty must be resolved at a chief-weight or coating-percentage boundary was located in the sources reviewed here. The control sits with the importer: require laboratories to report method precision, and escalate any confidence interval crossing the boundary.

Does chief weight also settle the statistical suffix?

Chief weight settles the material attribution a heading requires; it does not settle the full ten digits. Subheadings are compared at the same level under GRI 6, and a subheading can impose a separate percentage threshold on a different denominator, as heading 5903 shows.

What if production drifts from a ruling's stated composition?

A ruling responds to the facts presented, so one premised on a stated composition speaks to merchandise matching that statement. Where production lots drift, the premise no longer matches the goods entered. CBP has warned that laboratory testing at importation can lead to reclassification.