The Amarr 2432 features heavy-duty 24-guage exterior steel combined with a 27-gauge steel interior to make this polystyrene insulated door one of the strongest and most durable. The 4-step insulation system includes tongue and groove construction, 2″ polystyrene insulation, weather-stripping, and a thermal break that provides a strong barrier from extreme heat and cold. R-Value 9.40