Unless you are a professional boarder the ABEC 5 bearings are about the best that you can use.
ABEC 3 Shielded Bearings,
Common bearing on new "middle of the road" type inline rollerblade skates and skateboards. Great for roller hockey and skateboarders that need to replace bearings frequently due to the conditions of the skating or skateboarding surface.
ABEC 5 Shielded Bearings,
An upgrade from most new inline rollerblade skates and skatebaords. Great for the hockey, recreational skater and skateboarder that wants that frictionless feeling. Most common upgrade due to the fact that the price is not much more then the ABEC 3 bearing. ABEC 5 bearings cruise very nicely and have a nice frictionless feeling.
ABEC 7 Shielded Bearings,
An inline rollerblade, skateboard or luge racer's bearing. ABEC 7 bearings are used by the serious skater who wants the best. The manufacturing of this bearing is difficult and costly. The tolerances are very tight and they have virtually no friction under the load of your weight. They are truly a nice bearing to experience for any kind of skater, skateboarder or luge racer.