The HVN (High Viscous Nylon) Liner is a critical insulating component in modern track fastening systems. It is a “U-shaped” or “L-shaped” plastic component that sits between the rail foot and the shoulder of the sleeper, providing a seat for the Elastic Rail Clip. Its primary job is twofold: first, it provides electrical insulation between the rail and the sleeper (crucial for signaling); and second, it protects the rail foot from the mechanical “rubbing” of the steel clip. HVN liners are made from a specific grade of glass-filled nylon that is designed to be extremely “tough”—it can withstand millions of cycles of high-pressure vibration without being crushed or worn away. The “HVN” designation often refers to a design that has a larger surface area or a ” High Viscous Nylon” of material in the wear zones compared to older GFN-66 liners. These liners are color-coded to make them easily visible to track inspectors from a distance. Drawing Number RT-3702, RT-3706 , RT-3707 , RT-3708 , RT-6938 , RT-6939 , RT-8751 , RT8752 , RT-8753 , RT-8222 , RT-8223