If you’ve developed several similar USB products, you might be able to get them all USB certified with only one test. Simple changes like product packaging, model numbers, connector vendors/model number, etc. can often be certified with only a few forms filled out. More extensive differences, such as changes to the microcontroller, PCB or RF hardware, may require a retest, but the ultimate decision comes from the USB Compliance Review Board (CRB). More information on what is and is not valid for Qualification by Similarity (QbS) for USB can be found at the USB-IF website.