i’ve owned one pair of persol sunglasses in my lifetime.  i bought them on my honeymoon around this time last summer.  we were in st. barts and i had a little extra cash per a wedding gift.  they were bit big for my face, but i didn’t really mind.  i went with the 714 model.  the ones that look exactly like the picture above but fold in the middle.  at first, the folding didn’t bother me.  i thought it looked cool.  i could take them off and put them in my front pocket.  after a month, the folding became a hassle.  every time i took them off they would self-fold and when i tightened the screw they became difficult to fold.  even the folds on the sides of the sunglasses would steal a hair or two if i wasn’t careful taking them off.  i sold them on ebay for about what i paid for them (nice to know they don’t lose too much value if you make a mistake).  i’ve been meaning to replace them with the 649 model (above) ever since.  now is the time.  i realize folding sunglasses are making a comeback (see new ray-ban wayfarers), but count me out on this one.  they’re not worth the trouble.