When in doubt, order your typical size. If your measurements are in between those listed in the size chart, pick the larger size.
Wrap measuring tape across the forehead, just above the ears, and around the back of the head or where you normally wear your hat.
Primeflex fabrics solve the problem of restrictive clothing by utilizing a patented spiral yarn that allows the fabric to stretch and recover without using water-absorbing spandex. Primeflex fabrics are quick dry and offer durability, comfort, and stretch without the weight.