Consists of a number of different materials base metals (non precious), plating and organic coatings and plastic side tips and nose pads. Nickel commonly used.
Made from various heated plastics, injection moulded to shape, skin reaction very rare, lightweight strong mechanically stable easily worked and relatively inert at room temp
(Nylon, Supra): Uses either metal or plastic or both to make up the frame and lens is held in position by nylon cord part of frame is invisible, and thickness is important
No obvious frame, lenses in position with metal or plastic sides and bridge making for a less obvious pair of glasses. Thickness an issue