Visible hat lines are my biggest bugbear. Unlike those with hair, a bald man has to choose his hat or helmet carefully to avoid the hat equivalent of "pillow scars". Given the state of the environment (and that fact that I'm a foreigner living in Taiwan, near the Tropic of Skin Cancer) wearing a hat while outside is essential, even in December. Here, I'm closer to the sun in December than my Canadian city is in June.I'm not partial to baseball caps because of the line on the back of the head. And because of the lack of hair, a loose hat will come off in any breeze so a hat needs to be close fitting, though not tight. I've got a wide brimmed hat that's great for outdoors, but it leaves a line that encircles my head and lasts for hours, so I can only wear it for hiking.I usually wear rock climbing hats worn backward because: (a) the only visible hat line a backwards climbing cap leaves is on the creases above the eyebrows, so the lines blend in with other wrinkles(b) they crumple and fit into pockets easily, unlike ball caps, and they wash easily(c) they look ridiculous turned forward except when rock climbing(d) turned backward, they look like the "African beanies" which are popular (think Jim Brown)(e) they fit under bicycle and motorcycle helmets and need not be removed when ridingUnlike what some have said in other posts, helmets I've worn leave lines on the head, so having an under-cap is helpful. Let's be honest: who really wants to walk around for an hour with indentations all over the head?