It is really worm hat. However, I bought Large/X-Large and it still fits tightly over my head. Either my head is just huge or the people who made this don't know what Large means. I think it might be my huge head.

It fits tightly around my head, but it stretches out with wear. However, it is really worm. I found myself sweating on few occasions even on really cold weather. I also noticed that when I have longer hair, it gets messy after I wear the hat for few hours due to my sweating. This is fine with me.