What head size is med and large?
TIM F I normally wear a 7 1/4, so, a large. Adjustment starts at 7 1/8 via velcro and goes to 7 3/4.
STEVEN W i wear a 7 1/4 and md/lg is too small. Go a size bigger if in doubt. You can cinch it down to size if need be.
DALE T I have a large hat and wear a 7 1/2 size.
The drawcord adjustment on the back allows you to cinch it up for smaller sizes. Probably down to size 7.
If you might wear it in cold rainy weather upgrade the size to the next larger and cinch it down when not wearing a watch cap.
One of the few hats that does not flip up when winds pick up.
The cinch down adjustment for head size makes this a great investment.