MH: O.D. wall is a rubber material
HM: O.D. wall is a metal case
MH(S)H: O.D. wall is metal with a reinforced inner metal case
Valve cover gaskets and head gaskets play pivotal roles in maintaining the proper functioning of the engine. The valve cover gasket prevents oil leaks and contaminants from compromising the lubrication and performance of the engine, while the head gasket ensures the proper sealing of the combustion chamber, allowing for efficient fuel combustion and preventing the mixing of oil and coolant. Both gaskets are critical for the overall efficiency, performance, and reliability of the engine.




d1, mm

In this kind of seal, wider tolerances are possible between the OD of the seal and the seal housing. Irregularities of the housing surface can be taken up by the resilient rubber layer on the outside of the seal. However, the rubber covered seal can be blown out under high pressure in a reciprocating application whereas, with a metal case, there is no such danger.
In conclusion, iridium spark plugs are a top choice for car owners who want to upgrade their ignition system and improve their engine performance. With their durability, efficiency, and reliability, iridium spark plugs offer a range of benefits that make them worth the investment. If you're looking to maximize the performance of your car and extend the life of your engine, consider switching to iridium spark plugs for your next tune-up.

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Rubber covered
Pressure - Many oil seals can only withstand low-pressure applications, so understanding the compression set of your components is key.