The replacement headgear attachment for the ResMed Quattro FX comes in three sizes: small, medium, and large. The headgear features a crown-shaped design and has attachment straps that go above and below each ear. There is no bulky forehead pad, so you'll be able to move freely with your Quattro FX headgear piece. Compatibility. This headgear piece is designed for the Quattro FX only: it will not work with ResMed's original Mirage Quattro design. Additionally, this is just the headgear: it does not include the headgear clips. Quattro FX. The Quattro FX was designed with the comfort of sleep apnea therapy patients in mind. The unobtrusive interface allows users a clear line of vision, and the comfortable headgear straps are flexible, allowing you to sleep in any position you find comfortable. Reviewers Tip: Make sure you heave headgear clips for this CPAP interface: you'll need them to tighten your interface. Fitting the ResMed Quattro Full CPAP Interface.