Flat rubber o-ring seal. A common replacement part, this seal sits between the top of the blade and the botom of the jar. Fits ALL Oster blenders, Osterizers and Oster Kitchen Centers. Also fits some Sunbeam models which use a metal drive pin. 10 GASKETS INCLUDED. It fits models that the outside diameter of the base of the blade is 2 3/4". Does not fit Pro, Master, or Versa models.