D3644 Narrow Light Steel Door Door Type 2 Lock Type Mortise 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 4-7/8 In. 37-1/8 In. 69-3/8 In.