Usage Information: Nasal Cushion size is indicated with an abbreviation (i.e., M for Medium, S for Small, etc.) in black on the left side of the cushion. A black arrow next to the size indictor helps to determine proper placement of the cushion in the mask frame. Any cushion size will fit on any DreamWear or DreamWear Gel mask so if you find you want to try a different size you can simply purchase a new cushion rather than having to buy a whole new mask.