I have used the “shallow” version of the Ultra Mirage for years. I can sleep in any position, and the mask remains firmly sealed. It does not leak. It is easy to clean and the headgear is washable. I gave the mask a rating of 3 because the shallow version is not available and I had to select shallow wide. The shallow wide does not seal as well as the shallow. Bottom line: superior mask, durable, and comfortable not matter if you sleep on your side or your back.