With the small adapter makes you look them independently, he simply reversed again the two pins and so can each headset with 4-pol. Connectors are now reused to any cell phone with jack. The build quality is solid and the plugs have a good time.
I like the variant with angled plug FiiO LU2 best alternative there is also the execution LU1 with straight plug. (Side note for Schäppchenjäger: Amazon offers no offers 9.99 currently clearly the best price on the net)