Twin-wall polycarbonate twin wall sheet is produced in 4mm, 6mm, 8 mm and 10 mm. These products provide high light transmission, good thermal insulation, high temperature resistance, high impact strength (hail resistance) and can have our min-dew coating which eliminates condensation and water droplets.Twin wall is the most economical grade of multi-wall sheet available; it comes with a 10 year warranty against yellowing and damage from hail.