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!

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 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.

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.