These are great sunglasses and a good value, although I am no expert in this area.  I only want  to add -- to save others the time and trouble -- that the size does matter.  I bought my teenage son a pair of 54mm glasses and they were way too big for his head (and he is a normal, 5' 9" 18 year-old).  I sent them back and the 50mm pair fit him perfectly.  There should be someway to measure one's face to fit these better initially -- and maybe there is and I just don't know of it.  So beware: size matters.