Of all the components that make up this Gasket Kit A the O-ring,15x2.5 has the lowest price.
On this parts fiche the Seal,valve Stem is the most specified component.
A sample from the products for the Gasket Kit A include: Pkg,head Cover (nas), O-ring,7.8x2.2, O Ring,69.8x2.0, O-ring,15x2.5.