Thanks LDH! I've never heard of SKF before.
SKF is one of the best, and many think the very best, re the design and manufacture of rolling element bearings and related bits such as bearing retainers.
So if you need wheel or gearbox bearings, SKF is a good thought - but be sure to get the correct internal bearing clearance grade.
Now to seals.
Rather, lip seals.
There's good and there's bad.
There's seals detailed for rotary sealing, with subsets as a function of peripheral speed (RPM x size)
For example, electric motor shaft seals for 3600 RPM motors can be a bit looser fit than those for a 1800 RPM motor with the same nominal seal size.
Rest assured that any All Balls seal will be a rotary sealing based design of unknown peripheral velocity consideration picked from some sub SKF source's simple sizing table.
So, an All Balls leaker could easily be a function of design and/or quality.
There's also seals designed specifically for axial sealing, such as forks and shocks would use.
SKF has come out with bicycle and motorcycle application specific axial seals, that are designed for low friction.
I've been told that Fox has been using them since last year.
High end motorcycle racetrack front end builders current and "in the know", have been using SKF fork seals in the recent past.
I've been told that the original range of available sizes was quite limited but has since been added to.
Fascinating stuff, eh?