IEC 60153-4:2017 specifies straight hollow metallic tubing of circular waveguides for use as waveguides in electronic equipment. The aim of this recommendation is to specify for hollow metallic waveguides: a) the details necessary to ensure compatibility and, as far as essential, interchangeability; b) test methods; c) uniform requirements for the electrical and mechanical properties. This edition includes the following significant technical changes with respect to the previous edition: a) expand and revise the operation frequency range for waveguides; b) revise the allowance of aperture dimensions; c) revise the test method for aperture dimensions; d) revise the equation of attenuation.