The 2251J is the Pro driver as you already know.Originally Posted by Zilch
The 2251J-1 is the Consumer equivalent with a frame color change (4348).
The 251J is the same driver with a mass ring and aquaplas added as previously mentioned in another thread (SK2-1000).
I believe I already posted the 251J specs but could be wrong.
SK2-1000 sitting right outside one of the Everest II listening rooms.