I have had a number of pairs of these sunglasses, 6 pairs over 6 years in fact, and have 3 pairs still. Here are my experiences...
1) Firstly these are cheap glasses so you get what you pay for. I buy them because they fit me and I have a bad habit of breaking sunglasses...mainly by siting on them. So the price is good for people who break, or even loose sunglasses.
2) The grey rubber parts at the ends of the arms do tend to come off after a while especially when wearing in warm weather. So watch out BUT you can of course just glue back on...
3) The nose rests do come off in the end... but after a couple of years. What you would expect for the price.
4) For one pair the arm broke...not sure why. They were not put under stress.
5) I have never ever had any delivery problems and always get te case.
6) They have an annoying emblem that you cannot remove in the top left hand corner. It is small though and only noticeable if you are looking for it or looking up to the left alot...
7) They are open to bending or adjusting (without breaking) if they dont quite fit your profile.
8) When the grey rubber arm end do stay on, the glasses stay on your face well, even during exercising.
Over all for less than £15 they are excellent.
Hope this helps.