Product review (4 stars): I'd like to see some kind of flexibility to resolve this ...
In the end the product worked as expected.  The connection pipe and the pipe in my wall are the exact same size.  I had to cut the pipe on my wall flush and cut slits in to the Flex Vent piece.  Then bend a lot, then bend more, more, more.  Eventually I hammered enough that it's not venting exhaust in to the room.  All that said, I just ordered a second one for my parent's house.  This time I know what I'll have to do if the vent pipes are the same size.  I'll still have to cut and hammer but maybe it will only take an hour instead of 3.  I'd like to see some kind of flexibility to resolve this issue.