I designed this for a friend who has his P1S on a shallow bench against a wall. He has 4 inch duct work, but only 2.5 inches between his printer and the wall. This vent maximizes air flow and provides a 4 inch exhaust, while only being 53 mm (2.1 inch) deep. It is also designed to provide to not interfere with 1-way or 4-way AMS hubs. The exhaust vent has a 4 inch OD and a 3.75 inch ID, and is 1.625 deep.
 

It can be attached several ways:

- Ten 10x3 mm round magnets. Best if all oriented the same way.

- Double sided sticky tape.

- Two #6x1/2 inch sheet metal screws. My P1S had some unused screw holes in the back panel.

I put some 1/8 inch foam tape around the inlet to prevent leaks, and used sheet metal screws to secure it. An exhaust hose that is not strain relieved can put a lot of torque on the exhaust vent. Magnets may slip, and double sided sticky tape may slip over time. I recommend using screws if you have the holes in the back of your printer.

I did not test this on an X1C, but I believe they have the same physical case as a P1S.