The main reason I bought the roof vent covers is the material that the roof vents are made off seems to get very brittle and subject to cracking after a few years of exposure to sun. Many reports of people finding them cracked from minor things when they get older like nuts falling from a tree, small branches, etc. The covers protect them from the sun, don't have the same issues with getting brittle and as mentioend above, allow you to crank them open and notr worry if it's raining. Also can open them on the way to the campground to move some air through the camper and not have it so stifling hot when you get there.