Valmet has developed a new centre plate, for the RGP68DD refiner, which minimise the free volume in the centre of the refiner. The new centre plate has been evaluated in trials with Norway spruce as raw material for production of TMP for printing paper at the Holmen Braviken Mill, Norrköping, Sweden. The new and old centre plate was compared by generating refining curves both by changing gap at constant production rate and by increasing production rate at constant gap. When the production rate was increased from 13 to 19 adt/h in the trial with the new centre plate, the power and gap varia-tions were reduced by around 70%. The new centre plate did not affect tensile index and shives content at given specific energy. However, the fibre length at given ten-sile index was somewhat higher and the light scattering coefficient lower with the new centre plate, which might be an effect of increased blow line consistency and less power variations. The large improvement of refiner sta-bility and the increased fibre length opens up for seg-ment design development aiming at larger specific en-ergy reduction.