The Rightline Gear Sport 1 Car Top Carrier is 100% waterproof and attaches to vehicles with or without a roof rack. Attach the carrier's straps to a vehicle�s roof rack or use the car clips to attach the straps to a vehicle's door frame weather molding. The carrier is made from UV protected PVC semi-coated mesh XT and Hydrotuff for maximum durability. The materials are sewn together for strength a nd then welded along the stitching to make the seam waterproof. The carrier�s ZipRight system locates a urethane coated zipper on the protective zipper flap where water cannot enter. The Sport 1 is aerodynamically designed to save money at the gas pump.