This clear (white) Silicone Seal is designed for use with all Forma, FlexiFit 431 (HC431) and FlexiFit 432 (HC432) Full Face CPAP Masks. Compatibility Notes: The FlexiFit 431 Full Face Mask uses only the Silicone Seal. The FlexiFit 432 and Forma Full Face masks use the silicone seal AND a gray Foam Cushion. About Cushion Sizes: The FlexiFit 431, FlexiFit 432, and Forma each use a single frame for all sizes; therefore, if you would like to change the size of your mask, you just need to purchase a different seal (or cushion and seal) size of the new size you would like to use. .