Here is a comparison between the OEM JK ball joints and Crown replacement ball joints:
(A review of the first post in this thread may be helpful.)
As you can see, the OEM JK lower ball joint has a larger ball, for more bearing surface.
The Crown's liner has a hole in the top, and grooves (grease groves?), just like the OEM joint.
The Crown upper ball joint is a slightly different design than the OEM joint.
It has a spring in the top that pushes on the white plastic spacer, which pushes on the pin.
The top cap on the crown is steel. I had to put it in a vise to hold it together because the spring has a high compression load.
The plastic liner and the housing bore have a 0.005" taper toward the bottom. Not nearly as much as the OEM joint has.