Classic Accessories 42183106 RV PolyPRO 3 Pop Up Camper Cover - 16-18 Ft. Triple layer top stops rain while venting moisture Triple ply polypro 3 keeps out rain and snow. Thick&#44; triple ply top and single ply sides protect An integrated air vent system combined with quick drying polypro 1 sides reduce wind stress and vent Adjustable front and rear tension panels and elasticized hem corners provide a custom fit Integrated rope attachment system and a provided toss bag helps reduce crawling under the RV