I just installed 3 of these AeroFlo vent covers, made by Camco. I really like them. They're a bit more aerodynamic than the single Maxxair cover that I had over the bath vent; these are vented at the rear and the sides, and the entire top half lifts (2 screws) for full access to the vent for cleaning.
We don't stop playing because we grow old...We grow old because we stop playing!
2004 Itasca Sunrise M-30W
Carson enclosed ATV Trailer
-'85 ATC250R, '12 Husky TE310, '20 CanAm X3 X rs Turbo RR
Zieman Jetski Trailer
-'96 GTi, '96 Waveblaster II