If you are tired of replacing the plastic king pin bushings every time you service your front end, these are a must! We switched over to these last year on our ULTRA4 car. These have kept the knuckles tight after lots of race miles. From smashing though rocks to landing on the front end coming over jumps. The install was pretty easy and strait forward. These are designed to be used with adjustable preload high steer arms, but they are working great on our standard spring preload style high steer arms. Great quality as expected from TMR products!