I've bought a nice sx2 rotor stem with normal size clamp a year ago, but didn't knew there was a difference between road and mtb sizes back then (stupid me), so figured it was useles with my bar (which I like to keep, it fits me well) a itm pro 260. By chance I stumbled on an interesting bit of info, that itm actually made the road bars in 25.4 too instead of 26.0! So I checked it, and it appears that the size is something in between - 25.8. Can I use these bars safely with the rotor stem? I'm a bit anxious because of the extremely low weight of the rotor - half of the mantis stem it replaces!

_________________
Rides:
1980 ALAN super record, full campa SR, under construction

05 Principia Ellipse SX

itm's 25.8 is generally accepted to be the same as other brands' 26.0. i dont know what manufacturers' tolerances of the bars actually are.
some companies also made bars in 25.4, but they are typically much cheaper bars, mostly for entry-level O.E.. I would assume that's the case with itm.
nitto and some other japanese-based companies may make higher quality 25.4 bars, a lot of (all?) nitto and SR bars are 25.4.
i would not use a 26.0 bar in that rotor stem designed for 25.4.