N120 140mm Optical-Glass Fisheye Dome Port ~with Removable ShadeNauticam optical glass dome ports are finely ground to the highest standard of precision and represent the state of the art in both manufacturing and optical technology. Different size ports are available to support a wide variety of lenses and housing types. Port extensions or adapters may be necessary for some ports and housings. This optical glass wide angle port has a diameter of 140mm and is part of the N120 port system. The port shade is