Product review (5 stars): Fixed my squirrel problem
I have had recurring problems of bushy tailed tree rats finding their way into my dryer vent.  Warm and cozy spot for nest building I guess.
I went through several conventional vent covers sold at the big box DIY stores, but they were not getting the job done.
I also tried covering the vent hole with wire mesh, but that just turned into a lint trap that was almost as bad as the rodents.

I eventually got around to trying this device a couple of years ago.
It has worked great.  No rodent incursions, no lint blockage.
It is not beautiful to look at and it is bulkier than I had expected, but it does its job reliably and well.