Pump/Motor shaft couplings transfer the motor shaft rotation to the pump shaft. Shaft couplings consist of two metal "keyway and geared" ends and a plastic sleeve. Once the metal components are attached to the pump and motor shafts you can slide the sleeve onto one shaft and slide the pump (or motor - whichever is easier to move) into the locking sleeve to align them together. The pump/motor adapter and baseplate combination simplify this process because the shafts will automatically align and thus you do not require any shims.