At first, when I had these, I thought it did what others' do: muffle sound, rather than eradicate it.
But after a few days of use, I found that I was inserting them incorrectly, and after I found a system, that is, to roll them into as small a "cone shape" as possible, they were amazing! It's just getting them to actually fit inside the ear canal; though not too deep, for health reasons. Provided your ears are clean, these are seemingly infinitely reusable, and even after a little experiment with heavy weights, they always seem to return to their previous shape! Truly indestructible!
I tend to suffer from very sensitive headaches when woken up unnaturally, and, I must say, these have alleviated the pain. You can still hear loud noises a little, but nowhere near enough the level to wake from sleep. These are brilliant. It's just knowing how to use them.