Review (5/5): Don't be scared off by the price.
It's damn near perfect. Fits great, doesn't leave a line around your head.
I'm not going to say that a waver "needs" this; it's actually pretty easy to avoid the line around your head with a durag/boo-boo cap combo, but if you have $35 laying around, go ahead and get this. I was hesitant because of the price, but if you are trying to be a serious waver, this will be a good investment. You can still wear a durag with it if you are going out. It does feel like it could slip off while you are sleep, but I still wouldn't let that deter me from buying one.
You probably need the small/medium. I wear a 7 3/4 hat (which is a decent sized hat) and this fits nice & snug without any pain. I have plenty of room to make it tighter if I want to. I was actually wearing it too tight initially.
Why are you still reading this? Go buy yourself a Tsurag!