This is a replacement for the Prusa Repbox black PTFE connector. This will allow you to connect a PTFE tube to the box without the PTFE tube coming loose or pushing it back into the box.

Prusa Slicer: Default settings

Required Parts: 
PC-M10
PTFE Tube 

https://www.printedsolid.com/collections/repkord/products/repbox-v2-3-prusa-orange-edition-mdf-complete-kit