18 tooth gear - Located on right side of printer in the 500 sheet tray paper pickup assembly
HP RU5-0088-000CN, Drive gear
HP RU5-0088-000CN. Type: Drive gear, Device compatibility: Laser/LED printer, Brand compatibility: HP, Compatibility: LaserJet 4200, LaserJet 4250, LaserJet 4300, LaserJet 4350