A waveguide flange is the connecting face of a waveguide. It can be rectangular, square or circular. The types of waveguide flanges have been standardized into two groups - IEC Waveguide Flange Shapes and North American Waveguide Flange Shapes. Most companies that develop waveguide products use one of these standards, as this allows waveguide products from one manufacturer to be used with waveguide products from another manufacturer.