On March 8, 2019, US Customs and Border Protection (CBP) posted the following notice and a fact sheet on its website:

To ensure that the Harmonized Tariff Schedule of the United States (HTSUS) is aligned with the Trade Facilitation and Trade Enforcement Act (TFTEA), which was signed into law on February 24, 2016, CBP has worked with the United State[sic] International Trade Commission and the United States Census Bureau to change HTSUS units of quantities (UOQ) that were previously listed as “X” to specific quantities, such as kilograms (“kg”), number (“No.”), etc.

The first HTSUS UOQ update was made on January 1, 2019, and converted all the dutiable ten digit statistical suffixes that previously had a UOQ of “X” to a specific quantity. The next update HTSUS UOQ update is tentatively scheduled to be implemented on January 1, 2020, and will convert all the remaining statistical suffixes with a UOQ of “X” to a specific quantity.

For additional information on the HTSUS UOQ changes, please refer to the document links on the right hand side of this page. Questions about this initiative should be emailed to 484f@cbp.dhs.gov.

In addition to the fact sheet, there is a table listing all the HTS unit of quantity changes as of January 1, 2019 here.