On the return flight I happened to an adapter, which you probably can as a model how something should actually look like hernehmen: Gold-plated connectors, mono / stereo matching on a channel, crackling Tightness of all connections and about three times as heavy and high quality. So: Stay away from the Billigkram! And still what: Most major airlines now provide anyway to "normal" on the stereo jack so that these adapters are rather superfluous.