Dust carts aren't a new thing but shop vac feet vary widely, even between the same manufacturer's models. These are connectors that fit the Ridgid NXT 16 Gallon 5.0 shop vac, model HD16400, and 2" Schedule 40 PVC. Friction fit so its easy to take apart if needed with a flat top so its easy to attach a piece of plywood with bolts/washers.
Included .step files if you prefer instead of .stl
The author marked this model as their own original creation.