This replacement 1 horsepower impeller is designed to fit Jacuzzi J Series spa pumps. May fit other Jacuzzi model pumps. This impeller is a new, OEM part, number: 05-3863-05-R. Dimensions: Outside Diameter: 3-3/4" Thickness: 15/32" (Outside thickness at outside edge) Thickness: 9/32" (B) (Inside thickness at outside edge) Front to Back: 3-1/4" (From end of shaft to front on intake) Inlet Outside Diameter: 2-1/16" Inlet Inside Diameter: 1-13/16" Shaft Cover Length: 1-1/2" Shaft Cover Outside Diameter: 5/8" (This is where the impeller screws onto the motor shaft)