As we frugally rv full time, we always learn something new, like the importance of rv roof vents and covers. Since 2009, we've lived in a travel trailer and a motor home, and now a 5th wheel - all about 30 feet long, with roof vents on top which is standard if you like to breathe!
We discovered many pros and cons about using the standard crank vents throughout our travels. We loved the ventilation, but found them useless on rainy days, always worrying they would blow off down the highway if we forgot to lower them. Also, I cannot emphasize enough how much I cringed at the sun in my eyes at 6am each morning!
Our travel trailer and current 5th wheel had three roof vents in the same locations (bedroom, bathroom and living room) and our former motorhome had only two (bathroom and kitchen) - so we are quite used to the ups and downs of these vents in various locations. After using these covers on our campers, what we've discovered is this: these affordable covers are all "pros" - there are no "cons" to these things!
We are the proud owners of these ventilation covers on all three of our vents - and what a difference! Darker one for the bedroom, light ones over the other vents - and fresh air all of the time, rain or shine........