Tunnel Liner is a highly flexible polyethylene geomembrane specially designed for high-performance tunnel lining applications. Solmax (previously GSE) Tunnel Liner consists of a black core layer and two white outer layers, which greatly facilities visual inspection ad is available in two fire resistance grades (B1 and B2). Whether used in a new design or retrofit installation. Solmax (previously GSE) Tunnel Liner provides a unique combination of security, sealing integrity and installation efficiency.