PFF5-5601G offers additional +0.5 of caster over PFF5-5601 and is a high performance option to PFF5-4601, and aimed at offering greater precision with improved geometry for people wanting the very best from their E46 or Z4. Testing during the development of this bush has indicated stiffness gains of 190% compared with the original rubber bush. This new part, fitted to the rear of the front wishbone has a hard anodised aluminium outer shell with one of our unique low friction polyurethane centre bushes. The poly/alu combination creates a low friction rotating bush reducing the forces acting on the arm. Lower arm deflection has been decreased by reducing the compliant material within the aluminium shell. Results are less movement in the arm under cornering and braking, improving steering control and feel. This bush is designed to fit the 66mm aluminium bush. Please ensure you have the correct size bush before fitting.