Almost all street cars come from the manufacturer with an anti-roll bar as it is a common part of modern suspension systems. However, they are designed to be overly soft for maximum comfort. An anti-roll bar does exactly what it says by reducing body roll in all situations. Every Dinan tuned anti-roll bar is built and tuned specifically for each BMW chassis. Lowering the amount of body roll keeps your BMW more level than stock (while still allowing just enough body roll) to improve mechanical grip. This improvement gives the driver a much more planted and confident feeling in every corner. Add a 21mm Adjustable Rear Anti-Roll Bar to improve grip and stability by reducing body roll. Adjustable with 3 positions on the bar for easy adjustment this Rear Anti-Roll Bar may be added to the Stage 1 Suspension System for those who wish to build their high-performance suspension in phases but it is designed for use with Front Roll Control System for proper balance on cars with less than 30mm difference between the front and rear tire width.