The original Laycock clutch assembly for the TR4A is no longer serviced, whereas the alternative Borg & Beck assembly is still available. If your TR4A is fitted with a Laycock set of components the entire Borg & Beck set should be fitted, even if only one component is in need of replacement (components within the sets cannot be mixed and matched). You will also need the longer screws (no.9) to fit the thicker Borg & Beck clutch cover to the flywheel.