This is the ValueSet that contains all the codes in National Drug Code (NDC) Value Set (http://hl7.org/fhir/us/carin-bb/ValueSet/FDANationalDrugCode) and National Drug Code (NDC) Value Set (http://hl7.org/fhir/us/carin-bb/ValueSet/FDANationalDrugCode). E.g. what you have to deal with if you get resources containing codes in either of them