These bearings are advertised as 1/8" or 3mm ID. But you get 15/128" or 2 .95mm, which if you use it for any rotary tools, won't work for that low precision. The photo shows that after the first 5 or 6 mm the cutter shank immediately jams and does not go any further. If the inner diameter was specified as 3mm, that would be perfect.