This thing is a solution to wet hiking boots the night before another hike...
It is a Y duct that will fit over the opening to a set of hiking boots, blowing fresh air down into them to move moisture out.
I've also added some other fittings for use with cooling parts, or just making a Y-duct (short).
This prints very well on an UP!, but I've also printed these kinds of things on a reprap. The Y duct has a bridge 8mm up, so use support.