This sleep mask is great in terms of comfort and function. I am very glad I purchased this. While wearing the mask, I can sleep well on my side, my back, and my stomach. I did not realize how much I needed to wear a sleep mask until I listened to the audiobook titled, “The Sleep Fix” by Diane Macedo. This book made me aware of how low level was interfering with my sleep. I have large windows without shades nor curtains that allow moonlight to wake me up. There are electronic devices in the room which emit light which appear to interfere with my sleep, too. My Fitbit slows that my sleep is much better in terms of quality and duration since I began wearing this sleep mask.