This paper describes the present state of the art with respect to rectangular ridge waveguide giving tables and data from standard waveguide sizes and constructional techniques for both rigid and flexible waveguide. The problems inherent in waveguide connectors are discussed along with the various methods for producing waveguide assemblies. The problems inherent with present-day waveguide standardization are also discussed. It is essential that a series of standard waveguide for high pressure operation and for extremely broadband operation (ridgeguide) be standardized. The latest RETMA miniature standard flanges are shown along with present-day thinking on a series of pressurized contact flanges.