This is a dust extraction port that fits the tilting router lift fence designed by Matthias Wandel. It is in two pieces, one side for the hose, the other gets screwed on the tilting router lift fence.
The side for the hose has an OD of 100mm, so it should fit over all 100mm (or 4in) hoses that are sold for dust extraction.
More informations can be found on my website:
I wrote in detail about this project on my website: http://www.ijon.me/2016/09/23/hose-adapter-for-dust-extraction/?lang=en
make sure to create enough layers on the outside, I recommend three or more.
Also do not push the layer height too high, I recommend 0.2mm or 0.25mm.