This fits Davey QB spa jet pumps and many others. 5/8 Booted Cup with 3/4" Ceramic face. 

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Replaces Mechanical Seals For:
Davey QB2001, QB2002, QB2501, QB2502, QB3001, QB3002

Dimensions:
Spring Section: OD of Rubber: 41.5mm / ID: 17.4mm
Ceramic Section: OD of Rubber: 35.5mm / ID of Ceramic: 18.95mm