Flex hinge is a spring mechanism that complements the hinge for attaching glasses to the frame. Temples in ordinary glasses are maximally opened at 100 ° regarding to the frame. If you try to open the temple more than 100 °, this can lead to damage or deformation of the glasses. The presence of flex hinges in glasses makes the temples more mobile. Spring hinges also holds open temples at 100 °, but allows them to open up to 150-160 °.
Thanks to hinges, the temple mount becomes more resistant to damage. Glasses with flex hinges retain their shape longer, while in ordinary glasses, sooner or later, distortion of the temples may appear. In addition, glasses with flex hinges are more comfortable to wear, since the spring mechanism makes the temples fitting more softer, avoiding the compression of the head.