How I got my bearings. Ha ha.
My first skates were Riedell R3s, which come with Kwik ABEC-5 bearings. At the time I understood so little about gear that I only ever caught snatches of people's advice about what to get. Having heard that ABEC-7 bearings were de rigueur-er for better skaters, I went to Jodi at Orbit asking for ABEC-7 bearings and being careful to say it exactly as I'd heard. Like speaking a foreign language from an index card, and what followed was like when you ask a French shop lady where the bathroom is: you get a tumult of conversation that you in no way understand, but you smile and nod. The upshot was, I walked out of the Orbit skate shop with two boxes of Bones Swiss
Well actually, I do skate outdoors on Kwik ABEC-7s that I got for free as a door prize. I had a set of ABEC-1s and the set of ABEC-5s, but I gave them away to other people to use for outdoor bearings. So those are all the bearings I know, I like the Swiss Bones the best for their performance and they're also easy to clean. Instructions for cleaning bearings TK!
Bearing size
Briefly, bearings fit on the axels of your plates. PowerDyne plates—the plates that Riedell skates are built with— have 8mm axels and take 8mm bearings. Certain fancy plates, like Snyders and Roll-Lines, have 7mm axels and take 7mm bearings.
Bearing rating
Bearings are commonly ABEC-rated from ABEC-1 to ABEC-9, which is a rating of the bearing's precision. The higher the rating, the more smoothly the bearing rolls. Smoother is theoretically better, because smoother means that the bearing is easier to push. Higher-rated bearings don't exactly roll faster, they roll more per push. So you can either skate faster on the same push, or you can skate the same speed with less push.
ABEC-1 or ABEC-3 bearings are usually sold for outdoor skating. Bearings get dirty pretty quick outdoors, and a dirty high-precision bearing isn't exactly high-precision anymore. So definitely do buy a separate set of bearings for skating outdoors, and definitely don't spend a lot of money on them.
A typical Riedell beginner skate package for indoor skating will include Kwik ABEC-5 bearings, intermediate packages will include ABEC-7, and advanced packages ABEC-9. The lower-rated bearings are theoretically "brakier" and easier for less advanced skaters to manage speed. Then in theory, you upgrade as you become more advanced and more able to manage your speed.
Something to consider, though, is that the ABEC rating system is not specific to skating, but generally applicable for a wide range of industrial applications with the highest-precision bearings—that's ABEC-7 or ABEC-9—required for machine parts that spin at 20,000 RPM, whereas your skate bearings spin at about 2,000 RPM. Which raises the question whether higher-rated bearings are going to make a difference for your skating.
This is the case that Bones makes in their article ABEC vs. Skate Rated, which is worth a read. Bones makes a wide range of well-reputed bearings, basically Reds and Swiss with variations like Labyrinth (sealed to keep bearings cleaner), Six (six ball bearings instead of seven, supposedly faster and easier to accelerate), and Ceramics (lighter, harder, and stronger than steel bearings).
