Το rain cover είναι για αυτό που λέει Γιώργο. Για προστασία από τη βροχή.
Τι διαφορά στην αεροδυναμική μπορεί να κάνει η υφή της επιφάνειας
"The majority of the aero drag from these helmets comes from the shape, which a cover doesn’t necessarily help with. In fact, in some cases the cover makes the helmet slower by blocking some of the through-flow."
The overall shape and design of the helmet determines how the air flows around it (or through it) more than just the presence or absence of vents.
Helmet covers are great for keeping the rain out, but no, they won't turn you into Tony Martin.http://www.bikeradar...nd-donts-48455/