A headgear system and/or an interface assembly incorporating a headgear system that, in some configurations, is configured to transform from elasticated or “stretchy” behavior to “inelastic” behavior at least in response to normal or expected forces encountered during the intended therapy. In some configurations, upon fitment to the head of a user, the system automatically adjusts toward or to an appropriate size. A headgear portion or assembly for use in combination with a breathing apparatus in some configurations is at least substantially inelastic and is three dimensional in shape. The headgear portion or assembly can comprise a plastic core and a textile casing. The headgear, or part thereof, may also have integrally moulded labels, connectors, adjustment mechanisms and/or grips.
