It is a Prusa bowden system for printing from a dryer box with several options as wall-passing, M10 and 1/8 BSP fitting.

You can choose your best option depending the 3D material than you have in home.

I made this mod without modifying the original Ztop of the machine.You only need to change the 2 M3x10 screws for M3x18 and add 2 standard or self-locking M3 nuts behind it.