The FDA has not linked product code MRK to any particular section of the CFR (Code of Federal Regulations). There are multiple reasons why this might be the case:

• The product code was created for a class III submission that does not follow the normal PMN or PMA path - e.g., for a device that falls under HDE (Humanitarian Device Exemption) or EUA (Emergency Use Authorization).
• The FDA has generated the product code for an existing Class III device, as a result of a PMA supplement that modifies the device in a way that it can't fit under the existing product code originally assigned
• The product code was created for internal use at the FDA, and not for classification or regulatory-related purposes.