Review on 27-30Ft RV Travel Trailer Cover - Breathable Anti-UV Camper Storage 320D Water Resistant Oxford, Windproof Buckle Straps Ripstop Fabric. by Justin Wallace

This repels water, but if you end up with any pooling, it will seep through. It is water resistant, but not waterproof. (That matters when you buy it because of a roof problem!) My camper was at the low-end of length for this cover and I wish I'd bought the smaller one as there's a lot of extra material.