Snugz Full-Face Mask Liners will fit all sizes of all nose-and-mouth masks except for the ResMed Mirage Quattro and the Fisher & Paykel Forma XL. They are also not recommended for under-the-nose style masks such as the Respironics Amara View or DreamWear and the ResMed F30, or total face masks such as the Respironics FitLife.