Yukon Performance steel spool for 9" Ford with 31 spline axles. Spool uses 1.785" journal bearings. Yukon performance spools are made from the highest quality materials to ensure high strength and long life in performance applications. Spools provide 100% power to both tires at all times and are a lower cost alternative to lockers. Spools are not recommended for street driven vehicles. Yukon Performance spools come with a one year warranty against manufacturing defects.