I wear a Simpson helmet in size XL, so I expect probably a Large or XL would be what I would need. SA2005 or M2005 or later. I'll be wearing a balaclava so I won't get it too sweaty!

I'm sure to break my personal land speed record of 150 but we'll see if 1.5 miles is long enough to reach the Boxster's theoretical top speed of 176...
Thanks!
Gary Samad
858-733-1286