Analysis
HTS 4812.00.00 covers filter blocks, slabs and plates, of paper pulp under heading 4812 (filter blocks, slabs and plates, of paper pulp).
Goods classified here enter the United States duty-free at the general (normal trade relations) rate, as do about 100% of the 225 tariff lines in chapter 48. Chapter 99 measures such as Section 301 or 232 can still apply on top, depending on where the goods come from.
It is the only US line under subheading 4812.00, so the six-digit code used by every Harmonized System country and the eight-digit US line describe the same goods; a foreign tariff or an exporter's invoice showing 4812.00 points straight here.
Goods from countries without normal trade relations pay the column 2 rate of 20% instead of nothing, so origin decides between free entry and a 20% duty.
Census statistics map these goods to NAICS 32212 (Paper Mills), an industry of 188 US establishments employing 42,893 people. That is the industry code a US manufacturer of the same product would normally use.