Wilwood 140-9838 BB REAR-W4AR 14.25Wilwood 140 9838 BB REAR W4AR 14. 25 AERO4 Big Brake rear axle kits replace the factory disc brakes and use the OE parking brake assembly as a compliment to front big brake upgrades on late model trucks and SUVs. High capacity braking from the AERO4 calipers, BP 10 or BP 20 compound pads, and oversized rotors are matched to the OE master cylinder output, ABS function, and individual vehicle bias requirements. Enhanced brake performance, increased