According to Announcement  No. 4 made by the Customs Tariff Commission of the State Council of PRC:
Effective from May 19, 2020, 79 items in total in the 2nd exclusion list will be excluded from the second round of additional tariffs on US goods. The items in the exclusion list noted as “ex” are subject to both HTS codes and particular commodities.
This announcement will be valid for one year. Importers can apply for refunds of any additional tariffs paid on goods in this exclusion list. The application for duty refunds should be submitted to China Customs within 6 months.
The official announcement can be found here.
Source: Customs Tariff Commission of the State Council of PRC