Not sure, probably because they're double-polarized glasses.
Important thing to know about polarized glasses: DO NOT SPEND MONEY ON POLARIZED GLASSES!!!!! Polarization is good, but when you're spending top dollar on Oakleys or Smith polarized glasses, its not the polarization you're paying for. You're paying for distortionless lenses. Its important, more often in sports, that you are able to see what's actually there. I.e. when I play tennis I put down my usual shitty driving sunglasses (which are polarized) and pick up my Wiley Xs, which have no vision distortion whatsoever. I don't want to be swinging at a ball that is somewhere other than where I see it.
My Wiley X XL-1s
The military guys here may be familiar with Wiley X, as they make most of the ballistic protective lenses given to the military today. Its great knowing that I can take a 12 gauge to the face at 15 feet and at least I'll be able to see after that.