Plug coupling systems with ISO plug contour as they are worldwide in the millions to find for hydraulic applications, show the following disadvantages: - the leakage rate during connecting is considerably. - the coupling under pressure can not or only with great difficulty and high leakage loss be connected. The target of these research and development activities is to design a prototype of a coupling system, that allows a leakage poor, elliciendly connecting under pressure. Indoing so the compatibility with the after ISO 7241 - I standardized plug system has to be ensured. After concluding this project further development to production maturity will be required for about two more years. Working and generally involved in this project are besides the main applicant, other Industrial companies and Research Institutes from different European countries. The applicants believe in very good chances to produce and marked european wide this new coupling system that provides an important technology lead.