The top left bearing is the stock replacement for a Ford axle and housing. Notice how small the bearing is compared to the other two. The bottom bearing is a large-style 9-inch bearing that is used for a 31-spline axle with upgraded ends. The larger bottom bearing is used in street-driven vehicles as well as more aggressive driving, like drag racing or autocross. The bearing at the top right is a huge bearing used for drag racing and is able to fit the giant 35-spline axles that support large displacement motors.