This seal replaces the "O" ring or "square cut" style seals
As it is cup or Umbrella shaped thus the name
On many applications it reduces oil usage and "Blue puff" on start up by reducing the oil loss through the valve stems. (next time I tear down my race car I will be installing these)
It is a very popular re-builders part as the valve and valve guide do not have to be perfect to produce the desired results.
Most good rebuild gasket and seal kits come with the Umbrella seals if they can be used.
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