The 328ic 19mm caliper has greater reach to grip the vented rotor (325i has a 9mm solid rotor. A Stoptech braided line replaces the two short hoses and an intermediate pipe mounted to the trailing arm. Bimmerworld's solid caliper guides replace the factory slider pins; bronze bushings replace the rubber bushings. They're exposed and require periodic inspection and greasing, a bit of required maintenance and an element of compromise for a street car; Bimmerworld claims significantly longer pad life and more consistent brake feel. Worth investigating.