Ever had insomnia? It sucks. I used to have it bad. Up three times a night to visit the bathroom. That was when I had a thyroid condition. I’m better now. But now I have to wear a CPAP to bed and if it’s light outside, then also a sleep mask. Quality is important to me. My CPAP mask had to be one with a very good seal. My sleep mask has to blot out light. Mind you, having said that, I have not yet come across a sleep mask which blots out all light while I am wearing a CPAP, as well. But the most important thing to me about a sleep mask is that the elastic holds, and does not go limp after a lot of washes.