Why use a Fel-Pro Multi-Layer Steel Cylinder Head Gasket? Because more power per cylinder, higher operating temperatures, and thinner head and block castings demand a modified gasket. MLS Gaskets are stronger, more forgiving, and capable of sealing despite movement between the head and block. Such motion results from: lighter, thinner aluminum head castings that are more susceptible to thermal expansion; computer controls that can dramatically increase engine output; reduced clamping force that prevents stress points and cylinder bore distortion.