Caravan covers are made from grey, heavy duty, breathable, non-woven, polyproplene material, comes complete with storage bag. This material is water resistant, UV stable and breathable but not 100 percent waterproof due to its breathable nature. The breathability allows moisture and damp to escape. A fully waterproof cover can actually cause overwintering dampness problems by trapping damp and condensation inside without means of escape.