Adjustability is crucial when it comes to tuning your street car's suspension. Our Ultimate "on-car" adjustable upper control arms for the rear of your GM vehicle have been meticulously designed with the best materials and components available. We have replaced weak areas with aircraft quality 4140 Chrome Moly steel and utilized TIG welded construction for maximum durability. These control arms feature high quality QA1 spherical rod ends for a smooth and quiet operation. The Teflon lined rod ends prevent metal to metal contact, eliminating unwanted noise. The on-car adjustability of our Ultimate Arms makes it easy to make pinion angle adjustments, whether in the garage or at the track. With UMI's unique Chrome Moly on-car adjuster, you can quickly lengthen or shorten the control arm length with just two jam nuts. Pinion angle adjustments are essential for improving track 60-foot times, increasing traction, and reducing wheel hop. The bind-free operation of our rod ends makes them a great upgrade for both track and auto cross driven cars. Trust only the best-QA1 for long lasting performance.