The crank spline has broken and damaged the “female spline part “ that slides onto the crank sorry about the delay having
problems with the site .
So you need the Centa nose part - Phil B probably has something otherwise its a complete new Centa/Compensator outer:
Part number - T120133 CENTA COUPLING OUTER SOFT RETURN - although I think MMC only have the complete Centa available still.
How are you repairing the crank spline?