I use them and think they are great. They only took 10 minutes or so each to install. I not only leave the vents open when traveling to keep fresh air in the trailer, I leave them open all year long. Its nice not having that musky smell after storing the camper in the off season.
I have used them for many units over many years. In Arizona leave them open a bit all year. Install furnace filter material, you will have to cut the material to fit, between the screen in your vent and the vent frame to keep the airborne dust out of your unit.
I too have them on my trailer and I like the fact that I can leave the vents open without fear of rain getting in.
However I do find that there is one setback to these and that is lack of air flow. Does anyone else find this as well??
I have them on every vent on our trailer. We have 4 all together. The vents stay open year round when we aren't actually camping. The thing I really like about them is they drawn a vacuum and suck out the stail smells when you are in transit, especially from the bathroom. We don't have the musky order from a camper that has been setting idle. They work great. I recommend them to every camper. I mentions the vent covers in an earlier post. http://www.campercommunity.com/foru...s/160-any-rv-modifications-you-care-list.html
When we took the RV (bludog) in for it's first oil change, they had a special on these Vent Covers. Installed two for us. No more flapping vent covers going down the road. Mercifully quick way to purge hot air (it will become summer again...don't worry). Now that I see how they were installed...I'm embarrassed. Real easy...no drilling into the roof required.