Product review (1 stars): cheap plastic melts
I wish I'd read other reviews before I bought this.  The plastic is thin and started melting as soon as I placed it over the heater vent; I had to remove it after about 10 seconds when I started smelling burnt plastic, and it's already slightly warped from that brief contact.  This would probably be fine for redirecting cool air, but it's totally unusable for a heater vent.