OEM style replacement alternator rotor/clutch shell with primary chain sprocket combo. Incl. ball bearing. Magnets are encapsulated in a stainless steel shell. This will help prevent magnets coming loose; which fequently happens with OEM equipment. OEM replacement reference 36791-84. Note: Replacement clutch hub ball bearing is separately available as 556626/36799-84. TECH TIP: On L84-90 XL Sportster the alternator is installed on the clutch hub. This was poor design. Excessive clearance between clutch hub bearing; mainshaft ball bearing and needle bearing between the two parts of the transmission shaft allows the clutch hub to cock sideways; enough for contact between stator and clutch hub. Grinding stator and/or clutch hub is sometimes done; but not recommended by MCS; to add clearance which reduces output. Better is installing new bearings. From 1991-on the alternator was moved and the rotor is run on the sprocket shaft. This fixed the problem.