This is a Genuine OEM part, not an aftermarket. Spindle Assembly part # 618-06978 and 918-06978.
5-7/16" OD Pulley, 6-1/2" Overall Height.
Shaft has 6 point star to mount blades with MTD style 6 point holes.
(Spindle 618-06978 918-06978) Cub Cadet: RZT-L54, L54KH, L54KW, S54, S54KH, S54KW, XT1-GT54, ST54 and XT2-GX54 with 54" deck. Used on: MTD: 13A7A1ZW099, 1417A3ZW099, 14A7A3ZW099, 17ARCACW099, CGT5426, CSLT5424, ZT-L54 and ZT-S54 with 54" deck