A standard of 40-mm thick insulated panels door panels comprise a double skin of galvanised steel (0.5mm) insulated with polyurethane foam infill which bonds to the steel for additional strength. Panel edges are reinforced with strong galvanised steel providing a secure mounting for the wheel carriage and hinge assembly, giving improved stability and long-term operation.Guide tracks are galvanised steel, purpose-made for each door installation. A patented connector between track sections ensures that the door moves smoothly, substantially reducing operating noise and wear. Steel lifting springs and cable are used to open the door and keep it open. Uprated springs can be fitted for frequent-use doors.