All of the ball joints are the same. The numbers mean nothing to us, but the 'A' has to face outwards from the linkage ball.

Hey, if you haven't already, go to helifreak and check out the Finless Bob video's in the Tech Room. They are awesome and will take you from building to setting up, tracking.....everything you'd need to know about your trex and he even covers radio programming and flying.

Good luck!
Skarn