The Airfit F10 Headgear is available in 3 sizes. The size that comes with the originally packaged mask is Standard. All sizes of the headgear will fit all sizes of the F10 Mask.
It is important to determine if you have the Standard headgear of the Standard For Her version. The standard version has blue accents on the headgear and the For Her version has a light purple color. If you have a For Her version of the F10 full face this Standard size will not fit. You will need to purchase the F10 For Her headgear specific to the For Her mask.