The MCFS (MCG Fire Safe) insulating gasket includes a PTFE spring-energized primary sealing element and a secondary sealing element. It adds fire service capability to the standard MCG design through the use of a secondary sealing element of high temperature resistant Mica, which can maintain a sealing performance while subject to a fire of 1500°F (815°C). Under this design, the PTFE spring-energized primary sealing element and secondary sealing element are both seated in the retainer of insulating laminate bonded to a stainless steel core, creating a fireproof insulating gasket.

Both seals of MCFS gasket have very good spring back, because PTFE primary seal has a spring inside to energize the resilience and Mica secondary seal is seated on the camprofile retainer. They require low bolt stress for the sealing. Second seal will be a backup seal under the normal environment, and it will work once the first seal failure during the fire.