DynaBase® PR is a modified bitumen sheet incorporating the features of a polyester mat with a blend of SBS rubber and high quality asphalt. It is used as a base/ply sheet over insulated systems employing a traditional fiber glass ply felt or over nailable substrates with or without a standard fiber glass base felt, such as GlasBase. It may also be used in multi-ply modified bitumen membranes and as the base ply when installed over a JM Roofing Systems insulation.