Some of our metal models have hinges with the built in FLEX system that allows the temples to temporarily open slightly beyond their normal open position when an opening force is exerted on them, and to go back to their original open position upon release of the force. This prevents the eyeframe from deforming and the temples from disadjusting, (i.e. remaining open permanently beyond their normal open position). When this happens, it causes the eyeframe to constantly slide down towards the point of the nose instead of remaining in place close to the eyes. Typically, the temples disadjust when the frames are taken off with only one hand, a very natural action for the majority of people. This action is rarely performed in a straight-forward movement, instead it is performed slightly laterally in a somewhat unconscious way. This causes one side of our face to press toward one of the temples of the eyeframe, causing it to open beyond its normal open position. Our FLEX system allows the temple precisely to open beyond its normal open position preventing the deformation of the eyeframe and the disadjustment of the temple. Our Stainless Steel models do not need the FLEX system because the temples are flexible enough to open beyond their normal open position and back in a natural way without the help of such a system while still preventing the deformation of the frames and the disadjustment of the temples themselves.