Organic VM and Microfiber VMC: The organic has the same VM middle layer of highly efficient particle filter media as the VMC. The C is for the extra carbon filter, which can act as a desiccant and help with some odors but does not contribute to the particle filtering efficiency. The test for Viral Filtering Efficiency is on the VM filter media only. Both products offer equal protection from microscopic particles, and filter inflow and outflow.