^^ to the few posts above... I've been using $20 plastic sunnies that apparently meet UV-A/B standards for the last few years but I aint too sure... my eyes still feel funny after flying for a while on sunny days - so it's either that or the air-vent blowing into my face dying my eyes off
Either way, all the previous posts swear by their serengeti's and for that price I couldnt refuse... so far it's early days and I'm impressed mostly with the clarity. (yes they are glass, Leadsled).
In the end you can take peoples advice on what glasses suit them and try applying it to yourself - but only you can decide in the long run whether forking out a bit of money for eye wear is worth it or not. Maybe I'll "swear by the S" when it comes to my 3rd pair of sunnies... or maybe I'll go back to a $20 pair...