This is an Ikea RÄCKA curtain rod holder: There are 2 parts to print as the inner diameter is different to fit the rod.
No screws are needed to tighten the rod inside the holder: the diameters are adjusted to tighten the rod.
The holder is designed for Ikea RÄCKA curtain rods. This means that you can set up your curtain rod without the need for screws. Simply insert the rod into the holder and it is firmly in place.