That's basically just 2 4" vent flanges butted together and held with nuts and bolts man. Same exact thing. And a shit load cheaper.
Just install these flanges where you want your hole and cut it after wards once they're installed to make the hole easy. Or use a contrasting colored marker from the material and trace the circle and you could cut it just a slight bit bigger and would make it nice and clean.
You could put some kind of draw string sock on the end if you wanted as well. Glue it from the inside of the flange up around the actual flange so it's nice and professional like.
These ones are on Amazon.
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