Well, I have not bought them before, but I have heard them from other people. You should know that the prices of this kind of sunglasses are kind of expensive, especially when you get them from the official stores. So maybe you can buy them on online shop. For example, you can buy them at http://clothing-and-accessories.become.com/jimmy-choo-anouk-shield-sunglasses-black--compare-prices--sc1503312739. In this place, they can provide you many different kinds of products what you like and you can just pick one pair depending on your own needs. For example, they cost about 350 dollars to buy them. Also, you can buy them spray which can be good to protect your sunglasses. Besides, you should know that they are UV protected, so that they can protect your eyes from the bright sunshine and the UV rays. Anyway, they have high reputation because of their good quality and function; maybe you can just have a try.
