Product review (4 stars): Low Tech Means of Saving on High Energy Costs
This works pretty well, easy to install, easy to flip from Summer to Winter.  Remember, only use this if you have an all-electric dryer, one where electricity provides both the heat and the motor that rolls the clothes around.  If you have a gas dryer, this would be unsafe.  It saves money because we are no longer allowing the dryer to counteract the action of our heat in the winter or A/C in the summer.