All Glasteel Cooling Tower Panels meet or exceed the requirements of: Glasteel Cooling Tower Panels (fiberglass reinforced plastic) are designed to withstand the extremely corrosive environments often associated with the cooling tower industry and are engineered specifically for use as louvers, stair enclosures and exterior casing. ASTM D-3841 – “Specification for Glass Fiber Reinforced Polyester Plastic Panels” CTI Code for Standard Specification, Bulletin STD-131 – “Fiberglass Reinforced Plastic Panels for Application on Industrial Water Cooling Towers”