The housing is for a rectangular hygrometer which you can place inside the Prusa Core One using either 20x5x2mm or 20x6x2mm magnets. Fits either left or right hand side of door, or any other place it will stick. No glue necessary to hold the magnets in place.
Hygrometer I used can be purchased at Amazon.com
https://www.amazon.com/dp/B07MCGDN5C?ref=ppx_yo2ov_dt_b_fed_asin_title
Magnets: Either of the two size magnets mentioned above. They are pretty common on Amazon.com
I noticed that the hygrometer isn't the most visible item to see through the tinted door, but that's the way it is.
I would suggest print the model in PETG. No supports necessary.
El autor ha marcado este modelo como su creación original.