The clutch pivot ball is the part that screws into your bellhousing that the clutch fork rocks/pivots on. If you see where past the hard coating into the copper or dull steel area of this ball or in extreme cases, if it has a flat spot, you should replace it for optimal clutch function. When this ball becomes worn your clutch will be harder to operate and less precise and if worn enough your clutch fork may begin to rattle.
This is a genuine Mitsubishi OEM part.