A combination device is a device with multiple components that serve different purposes. Typically for a combination device, it is reviewed by the department in the FDA based on its primary mode of action. Sometimes the primary mode of action is unclear. In that scenario, you would file an RFD, request for designation, to the FDA. It would only be class I, II, or III if it were being reviewed by the CDRH. If the primary mode of action was drug delivery, it would be reviewed by CDER. After the device is designated and the primary mode of action is determined, you can than continue through the approval process for the respective department of regulatory affairs at the FDA.