Product review (5 stars): Easy retrofit, works great!  Why pay 2x for Heartland?  Buy spray foam to seal around your vent pipe
My dryer was pumping out freezing cold air all the time due to the cheap plastic flapper always getting stuck.  This thing has made a huge difference!  I can't believe people are paying 2x as much for the Heartland version.  I'm sure the plastic is better, but at twice the price it can't be worth it.

Install was simple except for using spray foam.  I was concerned about it not having the pipe, but it's actually better that way.  Most people are ordering this to replace their failing one which already has the pipe.  My cover just crumbled apart leaving the perfectly flush pipe.  Perhaps just as important is that I found there was a large square hole in my wall which wasn't insulated at all, so it was like having a 4" square hole piping cold air into my building.  A can of great stuff (which is horribly messy and won't spray upright, but "horrible stuff" probably wouldn't sell as well) sealed that up tight as a drum.  I waited an hour for the foam to expand then installed this temporarily.  I came back another hour later and it had gushed into the pipe area, so if you use foam plan on coming back the next day to trim and do the final install.  It is a pain that it needs to be painted, but I can understand that would raise the price a lot.  The four holes almost lined up exactly so no carpentry required.

I'm mildly concerned that the plastic floating cap that blocks the vent may get some lint trapped and not seal completely.  I don't see a better way of doing it since there's always a chance lint will attach itself.  I only just installed it so I'll have to update it after a few months to see if it gets lint caught there.  I would plan to check it each winter.  The good news is the top is separate from the 90 pipe so you can easily access & clean everything.