I've been on CPAP treatment for over 16 years now. Various design and control macchines as well as different types of masks. I centered on the nasal pillow a few years ago, primarily for comfort but also functionality. However, I discovered that I would breathed through my mouth which would get very dry and through a bit sore. A chin strap was the successful solution. It took a while to get used to th he chin strap which kept my mouth closed and breathing through my nose. It took a while to get used to this setup but it works. I sleep as designed. Put on the chin strap and the nasal mask without any thought and sleep soundly. Highly recommend this combination. Often wondered why Resmed or Phillips haven't built this into a mask.