Makita 2012NB dust collector adapter to insert a 44mm connector for a Festool dust extractor. You can still use it with a 50mm diam (DN50) dust collector hose (outer diameter of the adaptor).
Be aware Festo have different type of connectors this is for the 44mm type.
Original was designed by: https://www.thingiverse.com/NV_WoodCraft
The author remixed this model.