The 21 categories of articles on the USML are:12
"ITAR Part 121 - The United States Munitions List". Department of State - Directorate of Defense Trade Controls. Retrieved July 6, 2015. https://www.ecfr.gov/current/title-22/chapter-I/subchapter-M/part-121 ↩
"22 CFR Part 121—The United States Munitions List". https://www.ecfr.gov/current/title-22/chapter-I/subchapter-M/part-121 ↩