Sway bar bushing, rear, BMW Z3 4 & 6 cylinder models 1997 on. Each bushing is blue molded urethane with the correct stiffness to improve handling response. Bushing is molded with internal spiral threads to hold lubricating grease thus reducing noise. Bushing has internal diameter of 17 mm and RACING DYNAMICS logo. Sold as each, you must order 2 for 1 sway bar. The bushings offered our for replacements of the Racing Dynamics sway bar kit for the model specified.