D3537 Flush Steel Door Door Type 2 Lock Type Cylindrical 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 4-7/8 in 35-1/8 in 65-3/8 in 38-3/4 in