When getting setup with a CPAP machine for sleep apnea, a provider may put out many different types of used CPAP Masks that have been used by hundreds of people to see which one fits best for the person. It's an effort designed to prevent opening up new masks constantly to cut on costs.
My dad went to the medical supply store to get setup with a CPAP Machine. When they put out the CPAP Buffet, he asked for a new mask.