Don't buy if you don't need to
These glasses are built cheaply and the cost kind of made me suspicious. The first time I wore two of the glasses  the bows were obviously loose. One had a loose spring and the other needed a screw tightened and a dab of glue added in hopes it would be sturdier. I've worn the third pair for a couple of days and it seems to be doing well. The fourth pair I lost, typical! So basically, they are just too cheap to get much wear. Good luck if you decide to buy.
Rating: 3 stars