OEM power head shaft for Gribaldi Salvia sickle bar mowers, fits all models with dual articulating bars. A pulley threads on to one end of this shaft and the other end mounts the articulating arms of the power head, the eccentric arm of this shaft caused the arms to rock back and forth providing the cutting action of this mower. If there is excessive wear on this shaft it may cause the section or guard bar to break near the blade heads of the bar