As a generic statement, look for a silk sleep mask.
While not often actually silk, they tend to be soft polyester and use fabric filler rather than near-credit-card-grade plastic. (I agree, I don't understand firm sleep-masks)
In the photos (I know they're photoshopped these days), look for the mask to actually wrap around the user's face, and look for photos that show the same material on both sides (so you can see that you're not getting a different material on the user's face-side). Look for a bit of gloss to the material so that it appears to be a nice silk-or-polyester. Look for the little plastic clip of an adjustable elastic loop so you can adjust the tension.
I definitely have had to play with the elastic tension to get a soft fit.
I have heard that, since polyester is carcinogenic, it’s unwise to have things in your bed or near your face for long periods of time that are made mostly of polyester. I would be a little concerned about a sleep mask sitting on my eyes and near my nose and mouth for 1/3 of my life.
This definitely qualifies as one of those things I often wonder "what were they smoking when the thought of this, and where can I get some?". I'd love to be a fly on the wall in pitch meetings or see The Sharks be pitched this. However, I love that you can just wake up in your nitehood, adjust to be on the on the go, and one more adjustment to rob the stage coach or money train with your gang of outlaws.
I've had three in that time due to accidentally leaving it in hotel rooms.
A test of a good mask is if you can see any difference with your eyes open or closed, and if you can feel your eyelashes touch anything if you open and close them. These are excellent and have a satin outer which slides around the pillow rather than coming off or moving.
They include ear pads to block out sound, but I find them a bit uncomfortable and never use them.
I remember several twitter threads about this and the clear winner was usually the Manta Sleep Mask. Doesn't push your eyeballs in, plus the eye parts are velcro-attached to the strap so you can adjust them to your face.
+1 to this one - I use it too. It really helps if you use blackout curtains in addition to it. Add in earplugs and some white noise source (I use a fan) and you can solve a large portion of your sight/noise problems at night.
I find that the pressure on my head over the course of a night, even with the fairly loose mask, is very uncomfortable and disrupts my sleep even more than the lights.
