The ResMed AirFit F40 is the smallest tube-down full-face mask ResMed makes, with a minimal-contact nose-and-mouth seal.
For the full breakdown, see our best CPAP Mask for Small Face guide.
Most full-face CPAP masks fit like they were designed for someone with a bigger face: the cushion swallows the bridge of the nose, leaks at the edges, and the headgear has to be cranked down to hold everything still. A compact alternative fixes that. The current benchmark in the small full face CPAP mask class is the ResMed AirFit F40, which ResMed calls its smallest tube-down full-face mask and positions as a minimal-contact, under-the-nose design.
Full-face masks cover both the nose and the mouth, so they’re the standard choice for mouth breathers and for anyone whose nasal mask leaks once therapy pressure rises. The F40 shrinks that footprint by sealing under the nose instead of over it, which keeps the frame away from the eyes and cheekbones while still covering both breathing routes.
What Makes a Full-Face Mask “Small”?
A full-face mask earns the “small” label from its footprint and contact area, not from the letter on the box. The AirFit F40 achieves it with an under-the-nose cushion, a tube-down hose route, and minimal-contact construction: less plastic against the skin, with the same nose-and-mouth coverage.
Small is not a universal size, though. Each manufacturer measures differently, so a small in one full-face model can fit like a medium in another. Fit depends on more than face length:
- Nose width and height — the cushion must sit under the nose without crowding it.
- Face length — the frame should reach the chin without overhang.
- Seal position — the cushion needs to center on the face, not ride the bridge of the nose.
- Headgear tension — light enough to be comfortable, firm enough to hold a seal.
The AirFit F40 at a Glance
The AirFit F40 is ResMed’s smallest tube-down full-face mask to date, built to cover the nose and mouth while taking up as little face as possible. ResMed’s official AirFit F40 product page describes it as a full-face, under-the-nose, tube-down mask designed so the sleeper can move freely in any position. Launch coverage from March 2024 introduced it as ResMed’s smallest full-face CPAP mask.
| Feature | What It Means | Why It Matters |
|---|---|---|
| Mask type | Full-face | Covers nose and mouth for mouth breathers |
| Fit style | Under-the-nose | Cushion seals below the nose, frame clears the bridge |
| Contact level | Minimal-contact | Less plastic pressed against the skin |
| Tube routing | Tube-down | Hose exits low, away from the forehead |
| Sleep position | Any position | No fixed posture needed to keep the seal |
| Model claim | Smallest tube-down full-face | ResMed’s most compact full-face offering |
| Market status | Current US listing | Official ResMed US page updated in 2026 |
No official retail price appears on ResMed’s US page, so street pricing from medical equipment suppliers and online CPAP retailers varies. Warranty terms were not specified in the official listing.
Fitting a Small Full-Face Mask: Steps That Work
Getting a small full-face mask to seal comes down to measuring, starting with the right size, and resisting the urge to over-tighten. Fit beats the size label every time.
- Measure from the bridge of your nose to below your chin — roughly 3.5 inches is a common small-size baseline in ResMed’s F20 guide, though every model measures differently. If you land between sizes, choose the smaller one first.
- Seat the cushion before touching the headgear. Center it under the nose with the lower edge closing below the mouth; the mask should sit straight, with no folds in the cushion.
- Tighten the straps only until the cushion