This replacement 1-1/2 horsepower impeller is designed to fit Jacuzzi J Series spa pumps. May fit other Jacuzzi model pumps. This is a new, OEM part, number: 05-3864-04-R. Dimensions: Outside Diameter: 4" Thickness: 7/16" (Outside thickness at outside edge) Thickness: 1/4" (B) (Inside thickness at outside edge) Front to Back: 3-1/4" (From end shaft to front at 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)