The IKO Film-On-Film SBS Torch-On Underlay is a fully bonded, torch-applied roofing Membrane finished on both sides with a thermofusible film. It is glass fibre-reinforced and manufactured from SBS-modified bitumen. Unlike the traditional underlays the IKO Film-on-Film is designed with a thermofusible film on both sides for ease of application, acting as an underlay or intermediate layer in a multi-layer torch-on bituminous roofing system.