NEW! - Expedition now features MARINEX Marine Grade Waterproof Roof made of woven boat cover fabric for improved performance and longer life. Marinex boat cover material outperforms plastic Tyvek tops in terms of breathability and longevity. Every RV owner knows that moisture can do major damage to an RV. With the Marinex top you get great protection from rain, dirt, UV rays, heat etc, and you get superior breathability. This means that if your RV starts to build up moisture under the cover it can evaporate and escape. This is not always the case with heavily coated, polypropylene or plastic based covers. Trapped moisture typically leads to mildew, mold and rot, causing major damage.. Marinex fabric was developed specifically for the marine outdoor cover environment, has withstood rigorous stress testing and meets strict quality guidelines. This makes it an ideal choice for the rooftop material on an RV cover. A perfect blend of waterproof, breathable and durable, Marinex will give you the protection and performance you need for the most critical part of your cover - the roof. Marinex is engineered to outperform any polypropylene or plastic roof material. Marinex fabric has been tested in an independent lab according to ASTM standards and is rated as "Excellent" in UV-Protection. Marinex blocks 98.5% of UV-A and 99.8% of UV-B rays which can cause significant damage to your RV. Warp and Weft tensile strength are also tested according to ASTM standards to ensure that the fabric doesn't fail at high stress wearpoints, and can withstand the weight of the sides of the cover pulling downward in extreme weather conditions such as wet and wind.