The JeePerf On-The-Vehicle (OTV) ADJUSTABLE Rear Upper Control Arm for Jeep Grand Cherokees (WK) and Commanders (XK)Improve your vehicles on and off road handling, traction, droop travel and Pinion angle with JeePerf’s adjustable Rear upper control arms.Featuring your choice of a heavy duty Spherical Bearing imbedded in Polyurethane, Polyhead or Heim joints, this arm is designed for comfort, full articulation, gas tank's skid plate clearance and long service life. Riding on these UCA enhances traction, ride quality and safety.When you flex your rear suspension over 2”, your rear axle must move forward and a little bit to the side to accommodate this motion, then get back to its normal position when the vehicle is at normal height. When you lift your Jeep 2" or more, the rear axle permanently moves forward and to the side at the new vehicle height. When you flex your suspension further, it moves forward and to the side even more, possibly rubbing the tire on the rear fender and causing accelerated tire wear due to it being skewed to one side. The vehicle's thrust angle will not be correct and bad handling, side to side bouncing and accelerated tire wear will result. The added height has another effect on the pinion angle of the drive shaft. It must operate at steeper angle which will introduce added vibration to the cabin as well as accelerated wear of the U-Joints. To lift the rear end of your Jeep properly, your rear suspension needs new geometry to accommodate the lift. This can be achieved by using adjustable control arms, adjustable track bar and adjustable swaybar links if using the vehicle with a rear swaybar. The adjustable control arms can be adjusted to move the rear axle back to the center of the wheel well. The UCA can also be adjusted to rotate the rear axle to achieve that normal pinion operating angle of the driveshaft again, thus enhancing ride quality and restoring normal service life to the rear drive shaft U-joints.JeePerf's SuperFlex UCA are solidly built using the very best materials and most innovative design techniques. Safety, functionality and versatility were paramount requirements when we were designing and building these arms.JeePerf's SuperFlex UCAs have improved design to clear the gas tank's skid plate at full droop. Our SuperFlex Rear Adjustable UCA, using its imbedded Spherical bearing in Polyurethane bushing design at the chassis side guarantees smooth, fluid operation with a comfort level not previously achievable using a regular bushing or a metal-on-metal bearing.The arm fully flexes to allow the rear axle's unimpeded free movement with its increased travel range. With their large adjustment range, these UCAs are compatible with your current OEM setup AND future lift plans. The Heim joints are upgradable so you never have to replace your UCA again.The JeePerf's SuperFlex UCA uses SOLID CORE bent steel rods and thick adjustment tubes that allow on the vehicle adjustment. We use heavy duty, XR rated, industrial strength, sealed and PTFE lubricated, Heim joints and steel spacers for attachment to the unibody mounts. The spherical bearings we use are large, heavy duty, industrial quality bearings that can comfortably handle some serious abuse. The bearings and Heim joints we use are specified to be permanently lubricated so they will need no greasing and will require minimal to no maintenance during their service life.With such an advanced, adjustable, versatile, upgradeable and flexible design, these UCAs have surprisingly a simple, bolt on arrangement. All you need to do is mount them proudly in place of your old UCA. What you will notice as first impressions upon driving with the JeePerf SuperFlex UCA: Tightened up yet easier and more confident handling. Your Jeep will feel as if you are driving a brand new sports car. Superior vehicle tracking and handling Quiet, smooth, controlled bump taking feeling that feel like gliding over bumps. The faster your speed is hitting the bump, the smoother it feels. Lane changes at speed will be quicker and more precise with superior straight line tracking You will get the side stance of your Jeep is improved and it is dealing with road obstacles more comfortablyThe JeePerf SuperFlex UCAs come in durable, powder coated Red finish with the elegant JeePerf logo on it.Four wheel alignment after installation is required.