Stevens Roofing Systems, Holyoke, Mass., has introduced gray Stevens EV roofing membrane. The PVC Elvaloy KEE (ketone ethylene ester) based-membrane meets the ASTM D4434-96 specification for PVC, and is available in 45-, 60- and 80-mil (1.14-, 1.52-, and 2.0 mm) thickness. Stevens EV membranes are based on Elvaloy, an advanced solid-phase thermoplastic modifier that locks itself into the molecular structure of the material, and cannot migrate from the membrane. This non-migrating polymer helps the membrane to maintain its flexibility, appearance and color after it is installed and exposed to the elements. The membrane can be mechanically attached, fully adhered, ballasted (with stone or pavers), or can be installed as a vented roofing system. The material is Underwriters Laboratory Class A rated and has achieved Factory Mutual windstorm classification ratings of 1-90. It can be used in new and re-roofing applications and is highly resistant to a wide range of chemicals, contaminants and pollutants commonly found in rooftop environments.