This product is supplied as a 100 uG pack size. The unit activity is reported on the lot specific Certificate of Analysis. See the link below to review a sample Certificate of Analysis: https://www.sigmaaldrich.com/certificates/sapfs/PROD/sap/certificate_pdfs/COFA/Q14/I17001-100UG-PW0000210321.pdf
For this specific lot, the reported activity is 76,000,000 units per milligram (1000 uG). The unit per microgram value for this lot is 76,000.