Product review (5 stars): My frozen things stay frozen
This works as they said it would.  If it is really warm or really cold (-10) the things in garage freezer stay frozen.  I found out I needed this the hard way.  This fall when the temps got below freezing at night my garage refrigerator freezer did not run and things in it were spoiled.  The kit was easy to install in about 20 minutes.  If you are handy (I am not) it will take less time.