Again what learned after I had tested with the first delivery of 4 Euro-extensions with 6 different euro plugs a very uncertain contact in the clutches of the exchange brought no improvement. As an engineer, one is interested in technology, so called in the VDE headquarters in Frankfurt. The specialist for plug (no joke) then informed me that Euro-couplings are not approvable and not allowed as an extension in Germany. Only Schuko couplings with earthing contact! Therefore, stay away from these extensions.