Sizing Information: Brevida AirPillow Seals are available in two sizes: ExtraSmall-Small and Medium-Large. All Brevida masks use a single frame size so any nasal pillow size can be used on any mask frame. If you would like to change the size of your Brevida mask, you can just purchase a different pillow size and fit it to your existing mask frame To determine the size of your current AirPillow, check the front of the cushion for the embossed letters XS-S for ExtraSmall-Small or M-L for Medium-Large.