I bought two of these, one for myself and one for my husband.  They just arrived today.  He tried his on and he says they fit fine on him, but on me, they keep sliding off my head.  I thought it would be the other way around because I have thick hair and usually find that his hats are too small on me.  But shipping was fast and we got it on sale.  Well, I guess my husband will have two pairs now.  We haven't tried it outside, so I can't speak for how warm it keeps your ears.