Product: Camco 45191 RV Reflective Vent Cover
Overall sentiment: negative
Customer reviews:
The adhesive to these is HORRIBLE!!  I use them for room darkening in our RV when camping and I was constantly having to put the back up because the adhesive does not stick well.  For room darkening however THEY ARE GREAT! 
 As others have noted, these covers will not stay in place. Mine fell off within an hour of installing. And they were installed per instructions. The design concept is just flawed. Expecting sticky velco pads to stay adhered to the cover, hanging upside down (vent cover) or verticle (door window cover) just does not work. Plus, they trap head, so the glue just softens and lets go.

However, rather than returning them, we are getting a bit creative using more heavy duty velco and sewing the pads to the covers.

So unless you want to try to find a way to make them work, don't buy! 
 Velcro strips do not stick well to the vent and the cover keeps falling down. 
 They don't seal very well. Lotsa light gets around it. 
 This the same as the door cover the velcro strips could be better. We bought this and the door cover the strips melt when it gets hot we went and got differents strips and work good ..but they tear easy.. 
 Cleaned where the sticky velcro is going to be with rubbing alcohol, let dry for 1/2 hour..attached, was around 70 degrees outside....2 hours later, both of them fell to the ground...had to 3m glue them to the ceiling, then the velcro became unattached to the shield itself.....had to 3M that as well................................................... 
 poor fit will not stick to the roof falls down every night finally had to tape it on to the ceiling do not recommend 
 This item is very cheap and is almost useless. It is irregularly shaped and fits poorly. I have thrown it away after only two days of trying to use it. You could easily make something yourself that would work 100 x's better. 
 why sell a product that the buyer has to purchase better velcro to make it stick????????  This is absolutely ridiculous!  It would be an easy fix for the manufacturer to LISTEN to the customer complaints about this product and require better velcro glue. 
 The adhesive that holds the Velcro to the meta frame is very weak. Find another product, 
 Too thin. Lets light come through it.