This vibrating rubber gasket comes between the motor housing and the jar.
It is a replacement part for the below units, but in theory also fits units that do not come with a wear strip.
Blendtec Professional 750
Blendtec Professional 800
Blendtec Q-Series
Blendtec Smoother
Blendtec ABC
Blendtec 825 Connoisseur
Blendtec 825 Space Saver
Blendtec Stealth 875
Blendtec Stealth 885
Blendtec Stealth 895
Also suitable for older Blendtec models which are not listed.