Keihin vacuum release plate o-rings for FCR and FCR-MX carburetors.
The vacuum release plate is the loose plate on the flat slide assembly that serves as sort of a vacuum valve to help regulate engine vacuum, particularly when starting.  It will also cause inconsistent idling when leaking or worn.
The Keihin float bowl gaskets are made from a rubber polymer that remains pliable even after many years of use.
It is made to higher standards and ensures only the best quality for an exact fit and proper function in all conditions.