The Bearing Number is SB 210 ZZ Made by GBI
I am pulling up that that thing is a 50x90x18mm bearing which is a bit odd size for a 90mm kart bearing generally I see 20mm width.
I would like to note when it comes to bearing performance on a kart application you really want a C2 Bearing but no one makes them, The next best would be a CN bearing (unmarked clearance is CN) and as clearances get larger for C3/C4. The reason for this is simple, kart bearings are generally 2-4k RPM and are axial loaded. Its far more important that they are not preloaded on the shaft or by the bearing housings. This means a C4 bearings has a higher level of clearance which isn’t idea for a karting application due to dynamic loading that occurs.
I would really suggest if its a 90mm bearing going to https://www.qualitybearingsonline.com/1250-502z-rhp-self-lube-bearing-insert-50mm-shaft-diameter/?fbclid=IwAR1KyQ9-eikyi5ATbtLJPf-2qMMq3n21lSKYOukAZ484vEyXo0WDCaY5x9M as it is the best 90mm bearing on the market (The only good one) other then the BOCA bearing option which is a Hybrid and that can be good or bad depending on a number of factors so I can’t say if its a better or worse bearing to be honest. There is alot of things at play when loaded like hertzian contact stress. This can lead to Ceramics actually wearing out quite fast due to hardness of ceramic vs steel races. The cage quality and material as well as the seals all play major roles in friction.
The RHP bearing usually sells for $100 in Kart Shops! So your welcome, but more importantly the RHP bearing is made to much better standard and its poly cage is to a MUCH MUCH higher standard then any other on the market for 90mmx50mm Karting Axle Bearings. This means the balls track true, less friction loss and much less loss in dynamic situations.
Please keep in mind that free spinning a bearing without load isn’t accurate to loaded friction numbers. The additional clearance of a C4 that will actually add friction on the track might make the free spinning unloaded bearing seem better due to skidding but I can assure you its not.
When it comes to lubricant karts peak 100mph around 1200lbs per ball on the outer race for a 50mm bearing (if my rough math is correct) or significantly less for a ceramic ball due to ball weight add in driver load + cornering load your usually alright to use an oil if you wish to do so. I personally don’t like the maintenance of dealing with oils and I don’t think they do as good of job when it comes to friction when loaded. My personal grease of choice right now is called Archoil 8300, its faster when loaded after break-in, it requires zero maintenance and the bearings get faster with time and will last for years at near or over maximum RPM the kart demands of them.