Easy to clip on, and they stay on firmly with clips that don't harm my plastic framed glasses.  The gray tint gives good protection from bright sun and doesn't alter colors, which appear clear and vibrant.  They are a little difficult to flip up without smudging the lenses, since they are so thin, but it's a minor issue.  While the seller offers several sizes, these clip-ons do not cover my entire glass frames, but it's close enough.  Anyways, these clip-ons are a economical alternative to prescription sunglasses.  The plastic case is handy and a good way to keep them clean when not in use.