I forgot that this comes with a sizing piece on the mask, which is terrific for most people, but not for me. It digs into my head because I’m a side sleeper and is bothersome. I had to use my old headgear at 1 night. With no XS nasal cannula, (includes a S, M, and L nasal cannula), I had to order those separately, and the wrong cloth/elastic headgear, it wasn’t a smart purchase for me.