You'll need to know what they mean by hybrid ceramic. Some ceramic balls are not what you need for any diff applications. They have a low co-efficient of friction, and will slip more easily than a steel ball, or a carbide ball. If the bearing is for the chassis, then the life of a properly specified carbide ball bearing is worth having. The rotational speeds of our stuff won't give you much benefit from carbide v steel, but the life aspect is worth a consideration. This is what is generally meant by the term they are using...
Hybrid means it should have a ceramic (more on that later) ball and a steel cage. Races will also be steel. The advantage of 'ceramic' balls is they are lighter and harder, so the contact with the races is reduced and the bearing can run at higher speed. They can also have a longer life than steel balls.
It's the ceramic that needs care. The ceramic we want is silicon nitride which is 80% less weight than a carbide ball, harder, takes a shock load well and lasts up to 10 times longer without damage. Any ceramic balls that are grey or white in colour are to be avoided as they do not have the strength we want, have a lower friction (leading to higher end loads on the diff to get drive) and can fracture under shock loads - we all tap boards on the track now and again!! As a general rule of thumb, silicon nitride balls are very dark grey, almost black in colour.
Having got that bit sorted, the next question is what the race material is made from, and what grade the bearing is. There's no need to aim for the highest grade as we can't use the tolerances it provides in our applications. Won't bore you with that bit now unless someone asks. The race material is relevant, and should be a corrosion resistant carbon steel, or a stainless steel like 440C. If it isn't one of those, don't take your bargepole anywhere near them!
If you can get any assurances about them in these general terms from the vendor, you will at least know what you are getting. I'm not saying cheap = crap (it could be bankrupt stock or a cancelled order or a back-door import of a good bearing) I am saying that if it looks too good to be true...
I hope that helps, come back if there's anything else we can shed some light on.
