Refining element

Apparatus for refining lignocellulose-containing material comprising a first stationary refining disk having a first refining surface and a second rotatable refining disk having a second refining surface, said first and second refining disks being mounted with said first and second refining surfaces facing each other in opposed relationship thereby defining a refining gap therebetween, said first refining surface including a plurality of radially extending first bars separated by a plurality of grooves and said second refining surface including a plurality of radially extending second bars separated by a plurality of grooves, said plurality of radially extending first bars including a plurality of first raised portions alternating radially with a plurality of first depressed portions, said plurality of radially extending second bars including a plurality of second raised portions alternating radially with a plurality of second depressed portions, said plurality of first raised portions being located opposite said plurality of second depressed portions and said plurality of second raised portions being located opposite said plurality of first depressed portions, said plurality of first raised portions having a first predetermined length and said plurality of second raised portions having a second predetermined length, said first predetermined length being less than said second predetermined length.