Depending on the manufacturer, I wear a Med or Lg helmet. I tried a Lg Revolver and it squeezed my forehead too much. Sent it back and tried an XL, same deal. Reviews on the helmet said that it seems to be made for a rounder head than some people had. I guess I'm in that group. I sent the XL back and got a 500 Classic 3/4, Lg.
It squeezes my forehead too but not bad.
Kinda bummed, I wore Bells when I was a kid and always loved them. Always fit perfectly. Guess my melon's taking a different shape in my old age.
2003 HD Softail Deuce 87k miles and counting
2011 HD FLTRU 45k miles and counting