Just to make it easier to tell which of the 2 parts you are looking at:
The newer 5458X universal fit yoke has a small amount of relief around the outside edge, and there is a little more relief in the hole for the flats to go farther in when assembling it.
Top: Traxxas Part Number 5458. Revo Diff Only
Bottom: Traxxas Part Number 5458X. Revo or Maxx Diff
