Just finished installing roto joint lower control arms today and I am impressed by the difference they make. I had already done the upper and panhard (also with roto joints) and these compliment them greatly. Very little nvh from the entire package and these completely got rid of any clunking sounds coming from my car. Doing the upper beforehand made the axle feel pretty solid but the stock lowers still didn't allow the axle to rotate correctly. With the new lowers the rear feels completely solid and predictable. If I ever buy a new mustang these will be one of the first mods done.