This hat is made out of really thin material.  It looks like high quality material and the stitching is good, but I didn't think it would work well at all given how thin it is.  I was wrong!!!  This thing, worn under my bike helmet, blocks wind and wicks moisture from my head.  It is absolutely great to wear when biking down to 35 degrees!  I should also mention that I have a big head.  2xl is what I usually wear and this hat fits but is not big enough that I would wear it alone--just as a sort of helmet liner.  I wish it per bigger...