This 2" o.d. non-adjustable threaded aluminum shock is carefully hand-built, serial numbered and dyno tested in our Boonville, Indiana plant. Each aluminum PRO twin tube shock comes with both bearings and a serial numbered dyno graph. This shock may be run shaft up or shaft down and can be used in a coil-over setup for 2 1/2" i.d. coil-over spring by using C320 coil-over hardware kit (sold separately) For those using 2.25" i.d. springs you will need the C340 coil-over kit.