Product review (5 stars): Just what I needed to save energy!!!
The very night after I installed this during winter months, I felt the whole laundry room warm up!  Can't believe how much heat was walking out the door before this!  No one imagines heat escaping right out of the dryer vent!!!  The retaining clip could be a bit more robust, but nothing a piece of duct tape can't take care of if it ever cracks.