When we purchased our 2015 Cornerstone, one of the things that I thought was lacking was a finished set of louvers mounted under the exhaust fans in the bathrooms. Most higher end coaches have these and I brought it up with Entergra personnel when I ordered my coach. At that time, there was apparently an issue with the vendor, who was worried about air flow restriction.
I was happy to see that it is now a standard feature on the 2016 Cornerstone and decided to order a couple of them to install on my coach. They install directly over the current frame.
Upon receiving them, there are a couple of things to know before adding them to your coach. First of all, the are not hinge mounted. This means you have to remove the decorative plugs and remove the screws to remove the louvers. This is required to clean the screen and fan. A bit labor intensive for me.
The vents are unfinished on the top side. If you decide to add them, I recommend that you apply a couple of coats of exterior satin gloss varnish (I used Minwax Helmsman) to seal the wood from any water or humidity issues
All in all, the do add a touch of class to the baths and I am happy I installed them. I am confident that Entegra will address the issues I have raised.