Monel-
This is the traditional metal used for most sunglass frames. Monel is an alloy containing nickel, copper, iron and other trace elements, with nickel being the primary component (at 63-70%), followed by copper and then iron (at only 2.5%). This material is pliable making it easy to adjust. It holds its finish well, however, it is more susceptible to corrosion and more apt to cause allergic reactions due to its high nickel content. 

Stainless Steel-
Stainless Steel is made primarily from Iron and Chrome. It is a very strong metal alloy. Stainless steel frames can be made very  thin and still maintain their strength and great flexibility. Like Titanium, it contains no nickel, therefore it is virtually hypo-allergenic and resistant to corrosion.

Titanium-
This is a premium frame material. Titanium is stronger, with twice the tensile strength of traditional metal  frames and is  48% lighter. Titanium is also 20 times more resistant to corrosion and is hypo-allergenic, due to the fact that it has no nickel. 

Aluminum-
While aluminum was once very popular, and is strong and light, it is not used quite as much, as it does not weld or solder easily and is somewhat difficult to adjust. Aluminum does have a very unique look and feel to it. 

Barrel-
The most commonly used type of hinge. Interlocking pieces found on the inside face of the frame are kept together with a small screw. Some adjustability is available with some models. Be careful not to lose the screw!

Interlocking-
Very similar to the barrel hinge, but the hinge is actually part of the frame itself. Usually found in plastic frames, the joint is molded into the frame pieces and there is no separate hinge pieces holding the frame together. Once again, try not to lose the screw!

Spring-
Spring hinges use a spring tension to press the temples of the frame closer to the sides of your head. This allows for a closer, more customized fit. As a result, models with spring hinges are usually more expensive, but they are probably the most advanced hinges money can buy. Many high-end models like Maui Jim and Revo have spring hinges.

Break-away-
These hinges are made from interlocking plastic parts that "break away" or separate when a significant impact from the outside occurs. If you've ever been hit in the face when wearing a pair of glasses, you may already know the damage the frame may cause to your face during impact. These hinges, found mostly on sport sunglasses, will prevent that damage from happening again, and in fact, allow the frame to absorb some of the impact to lessen the blow directly upon your face.

Ultraviolet Protection: ( UV )
You may have already heard about the horrible effects of overexposure to ultraviolet radiation: Melanoma and skin cancer, increased risk of cataracts, etc. Thankfully, ultraviolet radiation is a high-energy, lower-wavelength radiation (higher than that of visible light, hence the "ultra-" in ultraviolet) and as a result, it is easily reflected. The ozone layer of the earth's atmosphere reflects most of the UV radiation from the sun back into space. Closer to the ground, we can rely on glass windows to reflect up to 90% of direct UV radiation, and special chemical coatings can increase this to virtually 100%. Thus, it is relatively easy to protect one's eyes from the damaging effects of UV radiation, just by wearing sunglasses! Almost every model we carry will deliver a near 100% UV protection rate. More specific information is available depending on the manufacturer and model.

Polarized Lens :

How Do Polarized Lenses Work? : Light reflected from surfaces like a flat road or smooth water is generally horizontally polarized. This horizontally polarized light is blocked by the vertically oriented polarizers in the lenses. The result: a reduction in annoying and sometimes dangerous glare.