Rotary 12659. MTD Spindle Assembly with Fittings, 5.0 Inch Diameter Pulley. Replaces Part Number 918-0428A, 918-0268, 618-0428, 618-0428A, 618-0268, 618-0268A. Length: 4.15" Pulley (PULLEY IS ROTARY 9588) end: 5/8"-18 Splined, Blade end: 5/8"-18 Star, Years Used: '98 to Current. Used on 50"