could you explain what are the differences ofthis bearings and pros/cons as well.
Mercury bearings
Abec 7
Yyj bearing
Thanks!
Oh as well as their maintenance.
I don’t know about the mercury or Abec bearings, but I can tell you they aren’t used much anymore. YYJ has two types of bearings: regular steel bearings and stainless steel (SPEED) bearings. The stainless steel are not immune to rust, but they are much less prone to it. Whether that’s worth the extra cost or not is really just up to preference.
Almost all bearings are maintained the same. Lubing and cleaning every once in a while.
Abec 7 - means absolutely nothing in regards to yoyos, just a steel bearing… no maintenance is ‘needed’ typically… but a drop of light oil now and then is nice to keep it running smooth
yyj bearing - bearing used by yyj heh… again steel bearings… maintenance see above
mercury - steel bearings that are stripped down to bare metal with an industrial process, leaving absolutely no oil or residue like normal cleaning methods do. Can’t really do much to them other than blow with compressed air or you’re negating the whole point… if you clean them or oil them they’ll be the same as a normal bearing. They don’t last as long as normal bearings since the bare metal will wear out over time.
Kyle
I really have no idea on the bearings except for the yyj’s, well not much. I’m wondering why and how bearings are rated or numbered like on ABEC. Thanks guys.
I’m surprised Kyo. I figured you would link to one of your rants on how people misunderstand the abec rating. I was actually hoping you didn’t post yet because I was going to! lol
Oddly enough, I do have better things to do than have that same argument over and over again 
It is usually enough to say the don’t matter… it’s when people who -think- they are experts weigh in that it becomes annoying.
As to the ABEC ratings question… the simplest explanation is that it’s a rating system based on series of tolerances that have no impact on yo-yo performance.
Kyle
Oh thank you.
I thought there was something special about those bearings.