Tornado Tre
The OEM Head Bearings for my 900 Tre are both SNR BB40825 top and bottom.
Bore 35mm, Outside Diameter 55mm, Depth 14.5mm (35x55x14.5)
In addition, the 1130 head bearing removal special tool also fitted my 900 just fine.
Anecdotally this appears to be the bearing used on several bikes...