My miter saw is the Ryobi TSS103T.
The inner diameter of the part that attaches to the miter saw is about 37.9mm (1.5 inches).
The outer diameter of the part that attaches to the shopvac hose is 55mm (2 11/64 inches).
I had to do just a little light sanding on the outside of the shopvac side to get the hose to fit.
The author hasn't provided the model origin yet.