This is a simple, compact solution to connect headphones to the Stereo Mixer 1U. I happened to look at a pair of airplane headphones and the spacing and proportions seemed somehow familiar. This turned out to be correct.
This was when planning a small system and it solved a problem for me, as I did not have space for both stereo outs and dedicated headphone outs (and wanted to connect inputs in serial).
A standard airplane adapter does not fit the spacing of the 3U MixUp but fits perfectly into the Stereo Mixer 1U! This is also the case for most 1U connections both horisontally and vertically.
I just wanted to share with you all in case it could be something of interest for anyone else!