This is my first experience with clip-on sunglasses so I don't know if this is the norm, but after using maybe 1/2 dozen times, the plastic on one of the clips just peeled right back so I can't use them any longer without damaging the lens of my new glasses.  They fit the shape of my glasses well, so it's unfortunate.  My only other complaint was the clip was in my range of vision a bit much.