I designed this adapter so I can connect my 2.5" Ridgid shop vac hose to the dust collection attachment for my Kreg Jig. The actual inside diameter of this adapter is 57.75mm (2.27"), this forms a nice tight fit on the vacuum hose.
I've included the openSCAD file in case you need to modify it to fit other hose diameters. The design is fully parametric and easy to adjust. Just change the bottom_inside_radius as needed. The "top" section connects to the Kreg vacuum adapter and shouldn't need to be adjusted.