Powerflex Front Wishbone Rear Bush, Aluminium Outer Caster Offset PFF5-5303BLKPFF5 5303 includes a CNC machined aluminium outer shell with an eccentric offset bore, increasing caster by 6. 5mm 0. 5deg, for better turn in response and in corner camber gain. By including the shell and reducing the amount of polyurethane material used, we have increased stiffness by a further 50% over PFF5 301 and PFF5 303, and a massive 250% over the standard OE rubber bush. The results are incredible, with minimal deflection under steering load