These 4 layer covers have an extra inner layer versus other covers to help repel moisture and increase perc time from the exterior while allowing the cover to breathe from the interior releasing mildew causing ambient interior moisture. Helps the Roxor cab from smelling musty in high humidity areas. The 4 layers won’t trap the humidity as they protect your vehicle finish from sun, dirt, dust, droppings, and other airborne pollutants that can harm a vehicle’s paint finish.