A disc recliner operatively coupling a seat back to a seat cushion to allow selective pivotal movement of the seat back relative to the seat cushion about a pivot axis extending in an axial direction, the disc recliner comprising: a first plate adapted to be fixedly secured to the seat cushion, the first plate including a first plurality of teeth disposed therearound; a second plate adapted to be fixedly secured to the seat back and rotatably coupled to the first plate, the second plate including a second plurality of teeth disposed therearound, wherein a tooth count of the first plurality of teeth does not equal a tooth count of the second plurality of teeth; a flex spline including a flexible wall having a third plurality of teeth disposed therearound, wherein a tooth count of the third plurality of teeth equals the tooth count of the first plurality of teeth; Characterised by a wave generator (28; 80) having an outer profile causing a portion of the third plurality of teeth to meshingly engage with the first plurality of teeth and the second plurality of teeth; wherein the wave generator (28; 80) includes a cam (55; 82) having a plurality of spaced apart lobes (56; 84) extending outwardly in a radial direction defining the outer profile and a plurality of rollers (60; 86) extending around the perimeter of the cam (55; 82) for direct contact between the lobes (56; 84) and the flexible wall of the flex spline for forcing the third plurality of teeth of the flex spline to meshingly engage with the first and second plurality of teeth (40, 48), wherein the second plate rotates relative to the first plate, thereby causing pivotal movement of the seat back relative to the seat cushion in response to rotation of the wave generator (28; 80). a first plate adapted to be fixedly secured to the seat cushion, the first plate including a first plurality of teeth disposed therearound; a second plate adapted to be fixedly secured to the seat back and rotatably coupled to the first plate, the second plate including a second plurality of teeth disposed therearound, wherein a tooth count of the first plurality of teeth does not equal a tooth count of the second plurality of teeth; a flex spline including a flexible wall having a third plurality of teeth disposed therearound, wherein a tooth count of the third plurality of teeth equals the tooth count of the first plurality of teeth; Characterised by a wave generator (28; 80) having an outer profile causing a portion of the third plurality of teeth to meshingly engage with the first plurality of teeth and the second plurality of teeth; wherein the wave generator (28; 80) includes a cam (55; 82) having a plurality of spaced apart lobes (56; 84) extending outwardly in a radial direction defining the outer profile and a plurality of rollers (60; 86) extending around the perimeter of the cam (55; 82) for direct contact between the lobes (56; 84) and the flexible wall of the flex spline for forcing the third plurality of teeth of the flex spline to meshingly engage with the first and second plurality of teeth (40, 48), wherein the second plate rotates relative to the first plate, thereby causing pivotal movement of the seat back relative to the seat cushion in response to rotation of the wave generator (28; 80).