A system for refining lignocellulosic material comprising: a bi-directional rotor plate segment comprising a first rotor plate refining area with at least one refining zone at a first radial distance range between an inner edge of the rotor plate segment and an outer edge of the rotor plate segment, the at least one refining zone having a refining zone length, and a bi-directional stator plate segment comprising a first stator plate segment refining area with at least one refining zone at a second radial distance range between an inner edge of the stator plate segment and an outer edge of the stator plate segment, the at least one refining zone having a refining zone length, wherein the first radial distance range and the second radial distance range overlap, the first rotor plate segment refining zone comprising a series of alternating bars and grooves, the grooves having a first rotor plate groove width, and the first stator plate segment refining zone comprising a series of alternating bars and grooves, the grooves having a first stator plate groove width, wherein the rotor plate segment comprises a second rotor plate refining zone at a third radial distance range between the inner edge of the rotor plate segment and the outer edge of the rotor plate segment, the third radial distance range being closer to the outer edge of the rotor plate segment than the first radial distance range, wherein the stator plate segment comprises a second stator plate segment refining zone at a fourth radial distance range between the inner edge of the stator plate segment and an outer edge of the stator plate segment, wherein the third radial distance range and the fourth radial distance range overlap, the second rotor plate segment refining area having at least one refining zone comprising a series of alternating bars and grooves, the grooves having a second rotor plate groove width, and the second stator plate segment refining area having at least one refining zone comprising a series of alternating bars and grooves, the grooves having a second stator plate groove width, characterized by the first rotor plate groove width being at least 50% larger than the first stator plate groove width, and the second rotor plate groove width being substantially equal to the second stator plate groove width. a bi-directional rotor plate segment comprising a first rotor plate refining area with at least one refining zone at a first radial distance range between an inner edge of the rotor plate segment and an outer edge of the rotor plate segment, the at least one refining zone having a refining zone length, and a bi-directional stator plate segment comprising a first stator plate segment refining area with at least one refining zone at a second radial distance range between an inner edge of the stator plate segment and an outer edge of the stator plate segment, the at least one refining zone having a refining zone length, wherein the first radial distance range and the second radial distance range overlap, the first rotor plate segment refining zone comprising a series of alternating bars and grooves, the grooves having a first rotor plate groove width, and the first stator plate segment refining zone comprising a series of alternating bars and grooves, the grooves having a first stator plate groove width, wherein the rotor plate segment comprises a second rotor plate refining zone at a third radial distance range between the inner edge of the rotor plate segment and the outer edge of the rotor plate segment, the third radial distance range being closer to the outer edge of the rotor plate segment than the first radial distance range, wherein the stator plate segment comprises a second stator plate segment refining zone at a fourth radial distance range between the inner edge of the stator plate segment and an outer edge of the stator plate segment, wherein the third radial distance range and the fourth radial distance range overlap, the second rotor plate segment refining area having at least one refining zone comprising a series of alternating bars and grooves, the grooves having a second rotor plate groove width, and the second stator plate segment refining area having at least one refining zone comprising a series of alternating bars and grooves, the grooves having a second stator plate groove width, characterized by the first rotor plate groove width being at least 50% larger than the first stator plate groove width, and the second rotor plate groove width being substantially equal to the second stator plate groove width.