Moog K80539 Control Arm and Ball Joint Assembly Problem Solver powdered metal gusher bearing design enables grease to flow through the bearing to the stud for reduced friction and enhanced strength and stability. Problem Solver patented cover plate design allows for tighter tolerances vs traditional cover plate designs, providing a more durable and extended life part. Exclusive cover plate protects against contaminants leaking into the bearing surface. Moog engineered steel composition results in a stronger component Full ball metal stud provides 36 degrees of smooth, consistent, rotational movement resulting in more responsive steering. Greaseable socket design allows new lubricant to flush contaminants from the assembly, reducing corrosion and wear