D3537 Flush Steel Door Door Type 1 Lock Type Mortise Material 16-Gauge Thermal Insulation U-Factor 0.41 Door Opening Height 80 in Door Opening Width 48 in Thickness 1-3/4 in Agency Compliance UL 1 1/2 Hour Fire Rating 6-5/8 in 37-5/8 in 68-5/8 in 34-7/16 in