This genuine Resmed part easily clips into place of your existing old F20 cushion, which over time will wear thin/small tears in the silicone will begin leaking air during use - making it noisy during therapy and disturbing you & your partners sleep ! This 'Memory foam' version is the premium version of the original silicone F20 and provides a greater mask seal with no sore marks left behind after use ! This full face mask is designed to provide a gentle, effective, reliable therapy experience, even when you move in your sleep. The AirTouch F20 is soft on your skin, easy to fit and comfortable to wear. This listing is for the MEDIUM size, and is compatible with all F20 masks (you can switch between the 'AirFit' & 'AirTouch' type without changing your mask & straps).