The major differences between the 405 and the FlexFit 407 are the new diffuser design and new Stretchgear headgear.Out of Box Solution. All Fisher & Paykel masks come fully assembled and ready to wear so there is no fumbling or confusion.FlexiFit Cushion. The unique inner foam cushion provides a secure seal. One standard size has been redesigned to mold to a variety of nose and bridge shapes.Frosted Silicone Seal. A frosted texture helps the outer silicone cushion seal against the skin.Glider Strap Anti-Leak System. This strap is used to connect the headgear to the mask frame for stability, but it slides across the frame when the head is turned so that the pressure of the seal stays uniform regardless of sleep position.

Bias Diffuser. The HC407 exhalation vent has be redesigned from one opening with a filter, to a series of several small holes that reduce noise and soften the release of the air. Filters are no longer needed.

Stretchgear Headgear. This new headgear design has an elastic section in the back that keeps the mask seal stable when moving the head up and down, as when moving from sleeping on the back to the side.