Product review (2 stars): Works better as a diverter, after modification.
I bought this unit to insert into the dryer's exhaust tubing in order to switch between the much better Indoor Lint Trap Filter I was also ordering, and the outside exhaust port (without using its included screen). The reviews on the Dundas unit were not good enough for me to use it exclusively as a filter trap, but as a diverter, yes. Great idea: exhaust heated air through a better lint filter into the basement during winter, exhaust heated air outdoors during summer by simply turning the lever. Great idea defeated: the manufacturer "improved" the unit by making a large hole in the diverter flap to prevent "blow back", thus defeating my purpose. To fix this problem, I cut out a round disc from a plastic lid and glued it onto the flap.
A trip to my local hardware store for more ducting revealed that they had a better made unit (sans flap hole) with a lower price (and no shipping). The unit now serves my intended purpose, albeit at greater expense and more work.