Grade 300 or Grade 25? Does it really matter? I'm getting ready to order some more bulk bearings for hubs and bottom-brackets. The easiest to get are those Wheels Mfg bottles from Jenson's with Grade 300 bearings. Are those ok for bike use? Should I really go the extra mile and search out Grade 25? What do most shops keep on hand for general use?

25 ... I get them from industrial Bearing suppliers["brick and mortar"] ,
less markup than thru the bike parts food chain..
. packaged in bags of a thousand.

25. No question.

What price difference are you seeing between 25 and 300?

Lately I've been buying through Boca Bearings, but I vaguely remember once buying one of those Wheels Mfg bottles. I don't remember if it was from Jenson, but I remember them being listed as Grade 300, but when they arrived it said Grade 25 on the bottle anyway. I just assumed that Wheels didn't bother stocking grade 300 anymore as the price difference is probably smaller than the cost of inventory overhead.

The "Grade" numbers for bearing balls are the deviation from roundness in .000001" (one millionth of an inch) increments. Grade 25 balls can be "out of round" by 25 millionths and Grade 300 by 300 millionths. Therefore the lower number is better.

Thanks everyone. @Metaluna, the Boca Bearings site looks helpful. Thanks for that.