My head measures 23-5/8" (60 cm) and I regularly wear size 7-1/2 brimmed hats, and after adjusting the band this cap fits comfortably with a little room to spare; it might be too snug for someone with a larger head or thicker/longer hair. Both of the colors (khaki, navy) are a little washed out in the listing photo--that's how they look in bright light/sunlight, but in more subdued lighting both colors are darker and the khaki has a noticeable green/olive hue. In the photo I posted I used my olive drab field jacket as a backdrop because most people have seen that color, and can use it for comparison to get a better idea of the true colors of the cap. The cap is lightweight and comfortable, and should be a good alternative to brimmed felt hats and/or wool flat caps during the hotter summer months.
That being said, the cotton material absorbs water like a sponge so this cap probably wouldn't be suitable for anyone wanting to use it to keep their head dry during a rainstorm, though I suppose it could be "waterproofed". Yep, that's my only "complaint", and I think it's a minor one.