The first regulator in the world with only one hose and the demand valve situated at the mouth.  The Cyklon was presented in 1958 and set a new world standard for diving regulators.  Still this regulator beats most other regulators on the market with some considerable ease.  The German Navy and many others still have the Cyklon regulator as their first choice, thanks to the well-tested construction and design.  It has been out in the field for over 45 years and experienced most of the things that can happen under the surface.