Analysis
HTS 3507.10.00 covers rennet and concentrates thereof under heading 3507 (enzymes; prepared enzymes not elsewhere specified or included).
Goods classified here enter the United States duty-free at the general (normal trade relations) rate, as do about 50% of the 14 tariff lines in chapter 35. Free here means free of the base duty only: origin-specific Chapter 99 duties such as Section 301 can still be owed.
The other lines in the same group are 3507.90.20 (pencillin G amidase, duty-free) and 3507.90.70 (other: other, duty-free).
Census statistics map these goods to NAICS 325199 (All Other Basic Organic Chemical Manufacturing), an industry of 894 US establishments employing 77,304 people. That is the industry code a US manufacturer of the same product would normally use.
All 2 neighbouring lines carry the same duty-free rate, so a borderline choice between them changes the statistics reported, not the duty paid.
Every edition we compared, from Jan 2023 to Oct 2026 (Rev. 22), shows the same general rate of Free.
Neighbouring lines
| Line | Description | General rate |
|---|---|---|
| 3507.90.20 | Pencillin G amidase | Free |
| 3507.90.70 | Other: other | Free |