Henry 608 33# Premium SBS Modified Glass Base Sheet is a high-performance base sheet for hot asphalt, cold process or torch applications, and is suitable for use over various combustible and non-combustible decks as the initial ply or multiple interplies for a specified roof system. This product is manufactured on tested fiberglass mat, impregnated and coated with SBS modified asphalt, and lightly surfaced with a mineral release material.