These filters slide in between the Diffuser Cover and the Elbow on all F&P Zest Q and F&P Lady Zest Q CPAP Masks. When in place the diffuser will lower the sound level of any F&P Zest Series Mask by approximately 5 dBA. The filter is placed under the plastic cover located on the elbow. The filter assists in ensuring the mask is super quiet and minimize exhalation draft. Includes the Diffusers Only, the Zest Q Cover is not included in this package.