TeraFlex HD ball joints are engineered to handle the increased load caused by oversized tires and offset wheels. The upper ball joint incorporates hard sintered wear bushings to handle extreme side load demands without failure. The lower ball joint features a threaded top cap for adjustable preload and allows grease servicing without axle shaft removal, even with larger RCV shafts. A machined grease passage in the lower joint housing assembly provides lubrication access without affecting the ball joint load surface. These ball joints fit 2007-2012 JK Wrangler Dana 30 and Dana 44 axles. This Kit Includes 2 Upper And 2 Upper Ball Joints WITH Knurl.Fits: 07-Present Jeep Wrangler JK 07-Present Jeep Wrangler Unlimited JK Upper Ball Joint Features: Extremely hard Sintered wear bushings to handle side load demands without failure Magnesium Phosphate coating to inhibit corrosion throughout 4140 chrome moly Ball/stud and a 1045 carbon steel housing Factory style serrated flange nut and grease fitting Lower Ball Joint Features: Hard alloy tool steel slotted wear plate for ball/stud to socket wear protection 4140 chrome moly ball/stud with magnesium phosphate anti-corrosion coating Factory style serrated flanged castle nut Adjustable end cap with lateral greasing access for easy on the Jeep servicing CR black Neoprene boot locked into position with both a spring as well as a spring steel ring Note: Note: Fits 2007-2012 JK Wrangler Dana 30 andamp; Dana 44 axles. We recommend ball joints without knurls as they will not score the inner knuckle and open up the bore. We also offer ball joint with knurls for ball joints that have a loose press fit in the inner knuckle due to repeated ball joint replacement or if knurled ball joints have been installed in the past SOME 2012 and ALL newer Jeep Wranglers come factory with larger front axle shafts Dana 30 and 44 than previous years, and will require grinding on the stub shaft forging parting line for clearance.