Size Small. These Nasal Pillows Sleeves are designed for use with all Swift II CPAP Masks. SIZING: The Swift II uses a single frame for all sizes, so all pillow sleeve sizes are interchangeable. If you are currently using a Small pillow sleeve and feel that a Medium might work better for you then you can just purchase a new sleeve in order to change the size of your mask. USAGE: For best performance replace every 3-6 months on average. COMPATIBILITY: These Pillow Sleeves have a solid front with an embossed logo. They WILL NOT work with the Swift (Original) CPAP Mask.