Adapter from Deik EV 660 2-in-1 vacuum cleaner to standard 34 mm accessories.
It was necessary to use the weirdly shaped almost-rectangular outlet of the vacuum cleaner on space-saver vacuum bags which have a circular connector, but should also enable the device to be used with any other standard vacuum cleaner tools.
Took some effort to get a nice transition from the almost-rectangular to the circular shape without introducing a smaller than necessary opening in between.
Model has 1 mm walls all around (so no infill), prints upright without support. At least on my printer, no special print settings are required.