Cometic's MLS (Multi-Layer Steel Head Gaskets) are ideal for both aluminum heads to cast iron blocks and aluminum heads to aluminum blocks. Two viton coated outer embossed spring steel layers with a steel inner layer that provides support to the gasket allowing multiple thickness. Withstands the shearing forces created by aluminum heads on cast iron blocks. Retains torque (once the gasket takes a torque set, re-torque is NOT required). Less clamping force is required allowing for reduced bore distortion.