This mount is specifically for a profile rig with 160x40 40series frame.
It is also specifically for this 880lb set of retractable casters.
https://www.amazon.com/gp/product/B08FDFJXK5
It uses 6 x M8x16 bolts and T-nuts socket head
And it used 6 x M6x12 and Lock-nuts Countersunk or Bevel head.
USE PETG ONLY 60% infill I used 6 layer wall thickness and 7 layers top and bottom.
This is using PETG in as a structural mount point, so please do not skimp on the filament.
The author hasn't provided the model origin yet.