I just put this hat to the test and it was awesome! It made a noticeable difference in repelling mosquitoes and gnats to the point where I sometimes took it off, thinking I didn't need it, only to have bugs return. I put the hat back on and they were gone again. (There were a couple times that I had to wave a bug away, when they came near my face where the hat didn't cover it, but I can live with that.) It also works great as a sun hat in intense, high altitude sunlight. It is breathable and kept sweat from running down my face without getting stuffy or hot. The chin cord easily detaches and reattaches.
I got it in white. The soil and sand I managed to pick up over a week of backcountry trekking came right out in the wash. It retains its shape after crushing, even when stuffed into a suitcase thrown around by the airlines.
My head measures 22-1/8"--right between sizes. I ordered the S/M size and it worked fine, not smashing my hair too flat, which is important for me as a woman. However, the L/XL would probably be a better choice if you want your hairstyle to stay as fluffy as possible under a hat. The cinch cords under the chin and on the back of the hat fine-tune the adjustment. (I didn't need to use the cinch cord on the back with the S/M size.)
There is no doubt that I would buy this hat again!