I have a Shimano 105 rear derailleur and am doing some spring cleaning. In cleaning the winter gunk from the pulleys I noticed that the jockey pulley (upper) has side to side play of around 1/8". The tension pulley doesn't move laterally.

I read this from Sheldon and thus the movement seems normal, I just wanted to confirm that a bit of lateral play is okay and that I don't need to replace it.

The upper pulley on a rear derailer. This is the pulley that actually guides the chain from one sprocket to another. Shimano jockey pulleys are designed with a "Centeron®" mechanism that allows a small amount of sidewards motion to compensate for imprecise index adjustment.

Thanks!