The price/quality equation for this cap is excellent, even considering the shipping cost. More important, the Spandex feature is both comfortable and utilitarian. I use the cap for golf and there is no slipping, while keeping hair intact (some caps seem to magically re-arrange one's hair somehow).
I wear a 7 1/8 hat size, but am glad I bought a Large. Medium for my size would have been a bit snug.