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.