D3644 Narrow Light Steel Door Door Type 1 Lock Type Cylindrical Material 16-Gauge Thermal Insulation U-Factor 0.41 Door Opening Height 84 in Door Opening Width 48 in Window Height 26 in Window Width 5 in Thickness 1-3/4 in Agency Compliance UL 1 1/2 Hour Fire Rating 6-5/8 in 39-5/8 in 72-5/8 in 40-15/16 in