After splurging on LASIK, my existing rx sunglasses weren't going to cut it, so I decided to get a nice pair of driving glasses.  Serengeti's reputation put them at the top of my list, and after giving up on finding glass lenses (where the reputation was established), I opted for this pair with plastic lenses.  I strongly recommend polarized lenses if your car has a sloped windshield, as the polarized lenses will help with that (some phones and navigation screens may be impacted by the polarization).  These have worked well, and the color does boost the contrast.  The photochromatic effect is subtle, but nice.  All in all the optics are great.  The size is subjective, by my size 7 3/4 head atop my 6' 7" frame likes the extra large fit.  YMMV.

My only negative, and it's impact depends on how much these are going for, is the cheap plastic sides.  I really cannot fathom why a pair of nominally luxury sunglasses wouldn't have something nicer.  That being said, I got these at a good price, and I'd do it again--the lenses are that good.