They are molded to my exact ears. I have tried several other ear plugs, and none of them come close to the level of isolation, including normal custom IEM's. Sometimes things are a little too loud (e.g. neighbors that won't quit on 4th of july at 2am), so adding white noise helps smooth things over.

I will say that I can very clearly hear my breathing with these in, as well as my heart beat sometimes. It's sometimes that bothered me for a couple of nights, but now it's quite comforting.