This is a wall mount housing for a RJ45 coupler.
26mm outer diameter.
It is designed for these coupler inlays:
https://www.amazon.de/gp/product/B07Q345W78?ie=UTF8&psc=1&linkCode=sl1&tag=croonentech-21&linkId=c2d09fdd50c3cb8ae5b60d787caf15a0&language=de_DE&ref_=as_li_ss_tl
Additionally needed:
1 step drill
(https://www.amazon.de/gp/product/B07Q345W78?ie=UTF8&psc=1&linkCode=sl1&tag=croonentech-21&linkId=c2d09fdd50c3cb8ae5b60d787caf15a0&language=de_DE&ref_=as_li_ss_tl)
2 screws M3x30
(https://www.amazon.de/gp/product/B07Q345W78?ie=UTF8&psc=1&linkCode=sl1&tag=croonentech-21&linkId=c2d09fdd50c3cb8ae5b60d787caf15a0&language=de_DE&ref_=as_li_ss_tl)
2 screws for plastic 2x8mm
(https://www.amazon.de/gp/product/B07Q345W78?ie=UTF8&psc=1&linkCode=sl1&tag=croonentech-21&linkId=c2d09fdd50c3cb8ae5b60d787caf15a0&language=de_DE&ref_=as_li_ss_tl)
The author marked this model as their own original creation.