one-eyed_jim
Old School Grand Master
If you've got the headset in front of you, there's no reason not to measure the balls you have. If you haven't got a Vernier caliper (and every cyclist should have one) place four balls together in a suitable groove and measure with a good steel rule.
BikePro is usually pretty trustworthy: their "5.5mm" balls equate to 7/32" . That's a fairly unusual size, but not unheard of. 5/32" balls are 4mm, near as damn it.
BikePro is usually pretty trustworthy: their "5.5mm" balls equate to 7/32" . That's a fairly unusual size, but not unheard of. 5/32" balls are 4mm, near as damn it.