Analysis
Subheading 5509.51 covers mixed mainly or solely with artificial staple fibers, within heading 5509. The first six digits are shared by every country that uses the Harmonized System, so this part of the code is the same in the US, UK and EU schedules; the 2 US tariff lines below it are national.
None of its 2 lines is duty-free at the general rate. Rates run from 9.7% to 10.6% with a median of 10.15%, so the line you choose sets the duty.
The US splits it as follows: 5509.51.30 for mixed mainly or solely with artificial staple fibers: single yarn… (9.7%) and 5509.51.60 for multiple (folded) or cabled yarn (607) (10.6%).
By Census's concordance, most of its statistical lines are made by Fiber, Yarn, and Thread Mills (313110). Those are the NAICS industries a US producer of these goods would report under.
Goods only reach 5509.51 once they fall within heading 5509 (yarn (other than sewing thread) of synthetic staple fibers, not put up for retail sale). Under General Rule 6, subheadings are then compared only with others at the same level, so a product is matched against its siblings, not against lines elsewhere in the chapter.
Tariff lines
| Line | Description | General rate |
|---|---|---|
| 5509.51.30 | Mixed mainly or solely with artificial staple fibers: single yarn (607) | 9.7% |
| 5509.51.60 | Multiple (folded) or cabled yarn (607) | 10.6% |