I've worn various sleep masks over the years, but this is the first one I've actually liked!  Despite its low cost, it's not even remotely cheaply-made.  The materials are quality, it's heavy enough to block out all the light while still remaining remarkably comfortable (after just a couple of nights it no longer felt like I was wearing it), it stays on my head all night, and, most importantly, it blocks all the light - lamplight, sunlight - everything.  The padded piece at the bottom of the mask ensures that no light can sneak in around the nose, and it also helps the mask stay comfortably in place.  If anyone suffers from insomnia and needs a few extra hours in the morning to sleep comfortably, or if anyone works the night shift and absolutely has to sleep during the sunlight hours, this is definitely the mask you need.