Heavy duty 14 gauge steel Filled up with polyurethane for energy saving Double pane glass, tempered and sealed to avoid conditioning leaks Included weatherstrippings to reduce air infiltration Operable glass panels that can be opened independently from the doors Thresholds made to prevent water infiltration Barrel hinges which are perfect for heavy use and can be greased for a better use Double doors include a pre-insulated flush bolt system to lock the dormant door or unlock it for a complete opening space