Originally Posted by Granpa

They are the roughly C shaped plastic bits that fit over the pins on the inner part of the drive axle. These ride in the slots of the outdrives. They are found on many touring cars and on some are metal, but these are too difficult to adapt to a Mini.

They produce a much smoother drive train and will prolong the life of your universals or cvds. I did this mod cause the out drives and the universals were constantly wearing out or breaking. Besides that they just look "trick"