MTD 917-0528A Worm Gear 20 Teeth Inside Diameter 3/4-inch, Outside Diameter 1-7/8-inch, KEYWAY: 3/16-inch, WIDTH: 5/8-inch MTD original equipment part 90-day warranty for defects in material or workmanship Fits 42-inch 2 Stage Snow blowers 2002-2005 and many more MTD machines