The BULLDOG trailer jack crank knob is designed for use with top wind series 139, 159, and side wind 170 trailer jacks. It is a genuine BULLDOG replacement part. Features: Fits all Bulldog sidewind and topwind jacks Black plastic knob Teardrop shape Includes hardware for installation Capacity 2000 – 5000 lbs. Series – 139, 159, Sidewind – 170, 90, Crown