Powerflex performance urethane bushings for the front diff mounts on the F80 M3 and F82 M4 will reduce differential movement under loading/unloading and give a more secure and direct feel to the rear axle. Performance bushings that are stiffer than stock do not all as much "wind-up" or deflection. Not only will these provide a noticeable improvement in performance, but they're guaranteed to last a lifetime!
Powerflex has extensive experience in automotive suspension and chassis systems and has combined these skills with advanced polyurethane manufacturing techniques. Durometer is standardized per fitment and location, so you can rest assured knowing the design engineers have selected the optimal urethane hardness for this specific part.
Note: Powerflex copper-based grease is supplied with every bushing set, and they will rarely need re-lubing due to the unique design features built into the material to hold the lubricant.