Selecting the right pair of motorcycle sun glasses is not as simple as seeing a pair and deciding you like them. You really need to look at the purchase of sun glasses as an investment in safety and style.
The purchase of your sunglasses does require some consideration, since quality glasses can be rather expensive. Some of the things you need to think about are price, quality, material, weight and structure.
Regardless of your budget, you need to decide how much you intend to use them, as well as what design will work best with your helmet. If you will be wearing them a lot, then you will need a sturdy material.
Some motorcycle sun glasses are made from plastic which is very light weight, but may not hold up too well. Others can be made from a variety of metals. One of the best metals is titanium. Titanium glasses should last for many years and are fairly light weight.
Also, you need to look at the level of protection your sunglasses will give you. Are the lenses shatterproof? What is the UV rating? The UV rating is very important if you are out riding all the time as UV rays can be very harmful to your eyes.
One more thing that is very important is the color of the lens. Browns tend to be better in bright daylight, and yellows are helpful in lower light. If you simply want a general use pair of motorcycle sun glasses, then you may want to look at a grey colored lens.