A headgear assembly for retaining a respiratory mask on a user's face includes arrangements or components that allow for variation in a size of the headgear assembly. In some configurations, the headgear assembly includes one or more hubs, each of which are configured to connect a top and rear strap together. The size of the headgear assembly can be determined by the size or configuration of the hub. In other configurations, the headgear assembly comprises one or more spacer elements within one or more straps of the headgear. The size of the headgear assembly can be determined by the size of the spacer element or a relative position between the strap and the spacer element.