Hi I got my CPAP in early 2016. At that time, the res therapist thought I needed size Small in the pillows. Accordingly, I have bunches of small pillows (ResMed Swift FX Bella Loops type mask). Early this year I decided to try one of the few Medium pillows I have. The fit was/is much better, and the whole experience has improved for me. I called my home medical supply store and asked if I could exchange the many unopened Small pillows for Mediums. The answer was No! Because I've had them for over 30 days. They told me they could sell them to me for $40 apiece, which I find ridiculous. I have found them online for $20 apiece, but that still seems over-the-top to me. Would anyone out there be interested in swapping some Mediums for some or all of the Smalls I have (16 total)? Please get in touch, if so. Thanks!