These filters slot in between the Q Diffuser Cover and the mask body on all F&P Pilairo Q CPAP Masks. When in place the diffuser will lower the sound level of the F&P Pilairo Q Mask to less than 24 dBA! This package includes 10 diffusers as well as a Q Diffuser Cover. USAGE: The Diffuser Filter and Q Cover help to make the F&P Pilairo Q Nasal Mask extra quiet. Diffusers and cover are not required for proper operation of the mask; but they are supplied as standard items with all Pilairo Q masks.