This print is intended for use with 45mm hollow core doors, but its threaded end allows it to also be compatible with the Ikea Lack table top or Ikea Kallax, which are 50mm wide. It can be adjusted to fit your specific needs.
I have personally printed it with a 0.28mm layer height and no additional support is required.
Why do you want door vent in your bathroom door?
If you have a bathroom exhaust fan to remove moist air after a shower, you should keep the bathroom door closed to contain the moisture within. Small vents in your door allow drier air to enter, making the fan's job easier.
Installation.
First, drill a small hole through both sides to ensure they are aligned. Then, use a hole saw, forstner bit, or spade bit on both sides (for the original size, use a 25mm bit). Next, insert the long printed piece from one side and fasten the short one from the other side.
I installed three vents on one door.
The author marked this model as their own original creation.