NAICS 33633 specifically excludes springs, which are classified under a separate manufacturing category reflecting their distinct production process. For HTS purposes, however, a suspension assembly that incorporates springs may still be classified as a complete suspension component if the spring is integral to the assembly — the HTS classification follows the essential character of the imported article, not the NAICS production boundary.

Imported aftermarket steering and suspension parts must be marked with their country of origin in a conspicuous location that survives normal handling, per 19 CFR Part 134. Parts that are substantially transformed in a third country before importation take the origin of that country, and CBP actively audits origin marking compliance for automotive aftermarket goods.