Steve -

Are you referring to the precision of the bearing? (ABEC 3 or ABEC 5?)

I would think that there would be a specified precision level, and ABEC 3 is probably fine.

(For a given bearing (for instance a 2302-2RS, common wheel bearing) you can acquire them from several manufacturers and several "ABEC" or "precision" levels. Level 1s are usually crap (cost $3 each), 3s are usually the "good" ones (about $15 each), 5s are getting expensive (but are certainly tighter, $40 each), and anything higher gets real expensive (I needed a level 7 for a milling machine, and it was well over $100...) You can usually get several levels from the same manufacturer, although the good ones (5s or better) are almost always German or US...)

-David