I've got one on an older frame I'm not using at the mo and it's very similar in size to a standard 1" HS.
Admittedly I've not changed the bearings. But I fitted it (and the one on my friend's bike) and there is no way it uses the same bearings as a 1 1/8" HS.
I asked SJS and they assure me it's the correct bearing for 1" or 1 1/8".
Which it almost definitely isn't.
Oh well.
Think I'll get her to fit a cheapo one until we can measure the bearing and order it.