The bearings on these are inserted into the aluminum blocks with what is called an "interference fit". What that means is that the holes that the bearings go into are actually a hair smaller than the bearing going into them. What we do is freeze the bearings and heat up the aluminum blocks to 200 degrees. This makes the bearings shrink a bit and the blocks expand a bit, and then they slip right in!
Once the temperature equalizes on both, those bearings are IN THERE! They will not move around or cause you any "clunking" noises. They are also held in by a keeper ring, to ensure they don't pull out of the bottom of the blocks.
These will only fit with coilovers. You will need our swivel bearing upper hat system to properly mate these to 2.5" ID coilovers.