Nice hat, cool idea with the little reflectors inside the dome to help increase warmth.  They actually work, the hat is a bit warmer than a traditional hat of this thickness.  Only downside - even the large/x-large is a little tight.  I am giving this one to my wife, as apparently my big head is a bit big for this one.  I'd say it is more Large than XL.

I have a Carhartt hat of a similar design that fits better, and I would recommend that if you have a big head.  I was looking for something very light to take backpacking but would still be warm.  The Carhartt hat is just about as warm but it is heavier and thicker.