After many years of blowing air onto my partner's back, F&P finally gave me a wonderful option. Not only does this diffuser stop the airflow, but makes the mask more quiet. Great design.
By Marty, Illinois
Swap out your elbow
If you have a F&P 407 that you love dearly (as I do) except that the elbow vent whistles like a firehouse siren in the night disturbing your sleep, order this from the F&P 405 with the filtered diffuser and swap them out (perfect fit). Quiet as a church mouse all night. By Ronnie , Marshall, Texas