The F2 Grease Duct Sandwich Access Door is for grease duct applications and meets NFPA 96 standards.  Its ceramic fiber gasket allows its use with temperatures up to 2300°F.  Please specify when ordering the F2 door for use with a duct wrap system - longer bolts will be applied.The F1 Hi-Temp Sandwich Access Door is for high temperature duct applications.  Its fiberglass rope gasket allows its use with temperatures up to 1000°F.