We have used MaxAir vent covers on our last three RV's and we are putting them on our new NL 8-11.
There are different types for diffrent vents. ( for Fantasic fans , for bathroom. Fans) we love them.
We can travel down the Hwy with our worrying about them getting sucked off by a Semi passing by, or by a huge wind gust.
We also like them because like people have said the roof vent covers get brittle and fall apart. Theses will give you som perfection if that vent cover happens to break / crack in the winter.
MaxAir vent coversGive these a try.
Soup.
2018 Northern Lite 8-11 EX Dry Bath
2017 Sierra SLE, 3500 HD / 4x4 / Duramax with a 6 speed Allison Trans
Torklift Super Hitch 20K, 48" Super Truss, front and rear frame mounted tie downs
Fast Gun Long Range SS Turnbuckles, Fast Gun locks