Adlens Sundial sunglasses, an incredible new technology at a great price. These glasses allow you to adjust each lens so that you can have great vision for whatever you are doing. If you have different magnification needs for each eye, need to change reading glasses because of lighting conditions or you are tired of buying readers as your magnification needs change, Adlens' Adjustables glasses are for you. Here's how they work. All you have to do is turn a little knob on the frame above each lens. Each variable focus lens allows the user to manually adjust to his or her needs for clarity. Each variable focus lens comprises an elastic membrane held in a chamber between rigid front and back polycarbonate plates. When fluid is injected into the chamber the elastic membrane bows outwards or inwards to change the power of the lens. Measurements are 49-22-141 MM. They are easily adjusted for a wide range of spherical powers from -6.0 to+3.0 - Incredible!