Using this as a headphone splitter while online streaming live events. Our sound mixer (xr18) only has one headphone jack, and we require two pairs of phones (50 Ω impedance, Sennheiser HD558), one for me at the sound controls, the other for the video engineer.
Previously, we used a slightly cheaper one-piece thingy from Bespeco, which was a piece of crap (one plug would not reliably connect, with a bunch of very audible clicking). Compared to that P.O.S., this one is well-made, feel solid, and looks like a sturdy tiny cable that you can rely on. The form factor with a short cable is also more appropriate than sticking a sturdy piece of plastic to the front of the mixer.
In short, an excellent and solid adaptor for connecting two headphones into a single jack.