FlintBoard® ISO Polyisocyanurate Roof Insulation features a closed-cell polyiso core integrally laminated to heavy, black (non-asphaltic), fiber-reinforced felt facers. FlintBoard ISO is approved for use under all major roof covering systems - built-up, modified bitumen, and single ply. FlintBoard ISO is offered in a variety of thicknesses, providing long-term thermal resistance (LTTR) values from 6.0 to 25.0. FlintBoard ISO is also available in 25-psi formula. FlintBoard ISO is the recommended roof insulation in conjunction with CertainTeed Commercial Roofing Systems including Flintlastic® Roof Systems.