Arrowglass IV is manufactured with a heavyweight fiberglass mat containing heat-cured resinous binders. The high strength glass mat is saturated with TYPE IV asphalt, giving Arrowglass IV excellent strength and weathering characteristics, as well as a uniform porosity for ease in application. Arrowglass IV is a ply sheet used in hot mopped roofing applications and may be the basic ply sheet used in all smooth and gravel surfaced roofing systems.