Helmet sizes in L XL or XXL do not mean anything. I usually select a size by the size in inch or cm if it is given, and then decide after I try it on. That's why I have never bought a helmet on-line. Usually, the AGVs come out a tad smaller and the HJCs a tad larger.
My Schuberth is an XXL, two of my AGVs are Ls, two HJCs are XLs. Go figure.