D3539 Flush Steel Door Door Type 3 Lock Type Cylindrical Material 16-Gauge Thermal Insulation U-Factor 0.41 Door Opening Height 84 In. Door Opening Width 48 In. Thickness 1-3/4 In. Agency Compliance UL 1 1/2 Hour Fire Rating 7-3/8 In. 39-5/16 In. 71-1/4 In. 42-7/16 In.