Section I Introduction This section of the standard pertains to pressurizeable contact flanges for use with rectangular waveguide as specified in the latest issue EIA Standard EIA-261@ Rectangular Waveguides (WR3 to WR2300)@ for the waveguide sizes WR90 through WR650. It contains a list of waveguide flange assemblies together with pertinent drawing dimensions. By specifying assembly dimensions in lieu of detail part drawings@ it provides for interchangeability and permits manufacturing flexibility with regard to the method of joining the flange to the waveguide.