I bought this to use with a Big Gulp Dust Hood. Turns out that the OD of the adapter and the Big Gulp were the same. However, the small end fits my Shop Vac perfectly. So instead of moaning and groaning about it, I simply cut a piece of sheet metal 14 3/16" x 2 3/4" and made a wide band clamp. Bend both ends 1" and 90 degrees for tabs. Drill 2 ea 1/4" holes for clamp screws and install to couple the two sections together. Bending the sheet metal to a nice round shape is easily done over a section of 3" PVC drain pipe. Elapsed time, about 20 minutes. Estimated cost, 15 cents, 27 cents counting nuts and bolts. Just as rigid as a friction fit, too.JB