Yeah, there are many fake designer sunglasses that mix into the authentic sunglasses. If they are fake, the manual work must be bad which can be felt by touch with hands or observation with eyes on the details. If they are fake, they may not be in balance when putting on the flat place to observe.
If you want to buy real calvin klein sunglasses, you shall check the sunglasses's logo and quality. Usually, fake calvin klein sunglasses are very cheap. They look very much like the original calvin klein sunglasses. But they are not real. So, their materials used are of worse quality. If you find a pair of calvin klein sunglasses that with poor quality materials and sold cheaply. They must be fake calvin klein sunglasses.
Yes, apart from the Calvin Klein sunglasses, other brands sunglasses also do have many fake ones. At the same time, we have to find some ways to tell whether they are fake or not when buying, otherwise, most of the famous brands will be end in the near future. As a sunglasses fan, I know some certain methods to tell, and now I will take the Calvin Klein sunglasses as an example, you can get the answer from the weight of the sunglasses, because we all know that the real ones are made from the high quality material while the fake ones are just made from the poor quality, the authentic Calvin Klein sunglasses are heavier than the fake ones. Also, this is the reason why you had better not buy online. Besides, you can also check the log carefully, if the logo is out of place or glued on, then there are much possibilities that you have bought, or will buy, the fake Calvin Klein sunglasses.
Yes, it is true that there exist loads and loads of fake sunglasses in the world and usually people tend to be tricked by those bastards who sell them. My advice for you is that before you make a purchase, you should carefully check the quality and some other things, including the certificate, the quality assurance and warranty. Besides, you might as well contact the after sales service to assure that they are authentic.