How do I know what size to get if I've...
How do I know what size to get if I've never worn a helmet?
The best thing to do is actually measure your head. If not, maybe you know your hat size for New Era.
7 1/4 = Small 7 3/8 = Medium 7 1/2 = Large 7 5/8 = X-large.
That may be a little off, but a nice thin skullcap will help make up the difference without sacrificing the performance.