I'm not sure. I wish that I could find one that would fit my husband. The extra large I thought would fit but he has a hard time with it. The headgear straps themselves are actually like too small so he can't get it to fit perfectly on his face and he's got a bigger nose so that's part of the problem too. But the strap is too small and he has been frustrated with it. He used it twice and it's sitting on his nightstand