Waterproof fabrics are fabrics that are inherently, or have been treated to become, resistant to penetration by water and wetting. The term "waterproof" refers to conformance to a governing specification and specific conditions of a laboratory test method. They are usually natural or synthetic fabrics that are laminated to or coated with a waterproofing material such as rubber, polyvinyl chloride (PVC), polyurethane (PU), silicone elastomer, fluoropolymers, and wax. Treatment could be either of the fabric during manufacture or of completed products after manufacture, for instance by a waterproofing spray.