This mount matches the internal diameter of my particular cat tree pillar, 60mm, to replace the broken mount. It stuffs inside the pillar and a bolt interfaces with the embedded hex nut. The friction fit of the mount seems good enough but you could add glue, maybe, or perhaps staples from the outside to more permanently embed this mount.

This print must be paused mid way through to place the hex nut (M8 maybe? It's 7mm tall and 14mm between flats) into the space, before the top of that chamber is printed. Use your slicer to do this, otherwise you just have to manually pause the print when it looks like it's almost done with that part.

Also note that there is a very slight taper to the outer walls of this model, so the top is slightly thinner than the bottom, such that it can be inserted easier beginning with the top.