Many people consider clip on sunglasses as a type of sunglasses but in reality they are merely a lens pair which is designed in such way that another pair of sunglasses could fit on the top of it. However, clip on sunglasses modify the entire pair of your original glasses. These are highly flexible, variable and erratic; and thus they are also called as clip on flip up sunglasses.
The best part about these sunglasses is that they have two separate lenses linked together by spring mechanism. Many eyeglasses with clip on sunglasses possess these features of spring and two separate lenses. These sunglasses are much inexpensive and anyone can buy them without any hassle. There are lots of varieties available into these glasses. You can also discern them on the basis of brand and quality.(Source: GlassesTribe)