Count on IKO for the best in APP modified bitumen roofing systems. IKO APP Modified Bitumen Roofing Systems are asphalt based and constructed of a tough non-woven reinforced polyester mat strengthened with select glass fiber strands treated with Atactic Polypropylene (APP) polymers to impart “plastic” type qualities. IKO Armourplast™ Classic and Armourplast Granular APP modified bitumen membranes may be used as either a cap sheet or a base sheet, depending on the application.