The US tariff schedule draws a classification line at 36% wool content within heading 620333. Blazers made of synthetic fibers but containing 36% or more wool by weight fall under the higher-wool-content lines, which may carry different duty rates than the sub-36% lines. Fiber-content testing and accurate mill certifications are essential, as misclassification at this threshold is a common audit finding.

Country of origin for apparel is generally determined by where the substantial transformation occurs — typically the cut-and-sew operation. A blazer cut and sewn in Vietnam from Chinese fabric would ordinarily be considered of Vietnamese origin. Supporting documentation includes cutting tickets, sewing records, and a manufacturer's affidavit. However, if the fabric itself is also formed in Vietnam, the origin case is even stronger. Importers should work with a licensed customs broker to document the production process, especially given the duty implications of Chinese vs. Vietnamese origin.