the factory style bushing articulate, or roll inside the arm making the travel up and down nice and gentle on the control arm, the after market or knock off arms have the bushing pressed into the arm so you will notice when you go and tighten it on the car and try to move it up and down it binds real hard causing the control arms to either bent, or you get one hell of a squeeky ride or even better you tear the bushings because you are forcing them to try and roll inside the ends of the control arm and they dont want to move. but, like you said, lifetime warranty, its a good thing you have lots of free time because you'll be changing it out often!