This is the ultimate, best-in-class torque biasing limited slip differential available. We ran the tests and the Pro Series was the clear-cut winner with respect to torque bias performance. Its higher bias design is defined by a 9° cone angle and higher spring load, which promotes a stronger lock up! The Pro Series allows you to get more of your available horsepower to the ground - where you want it! All Auburn Performance Differentials carry a 1-year warranty and 4-years of replacement exchange coverage. Made in the USA.