The Wilwood AERO4 Rear Kit 14.00 Drilled 2007-2011 BMW E90 Series with Lines is a high-performance brake system designed to improve the stopping power of your BMW E90 series. It features Wilwood's AERO4 four-piston calipers, which are designed to provide superior stopping power and fade-free performance. The kit also includes drilled rotors for increased cooling and improved response time. In addition, the kit comes with stainless steel brake lines for improved brake fluid flow, as well as mounting hardware for easy installation.