The O-ring,25.5x2.5 is the lowest priced item on this Gasket Kit A schematic.
Parts such as the Gasket Kit A: Pkg,head Cover (nas), Gasket,carburetor, Seal Valve,stem, Gasket,exh.pipe (nas) are included in the Cb250 Nighthawk 1991 (m) Canada / Kph Gasket Kit A parts fiche.
In this schematic the "Seal Valve,stem" is used most often.
