I'm interested in buying some myself, but when I think about all the possible sizes it makes me very nervous I never had to change ball bearings on any of my bikes. I maintenance them regularly, so I guess it keeps them in good shape, and there is no need for replacement...so far..so far lol
It blew my mind when I learned that same hub may have 2 different sizes. I don't have caliper to check the diameter...that may the biggest reason why I'm so nervous when it comes to ball bearings