A blade set assembly (116, 216, 316, 416) for a hair cutting appliance, the blade set assembly (116, 216, 316, 416) comprising: - a stationary blade (134, 234, 334, 434) having stationary blade teeth forming a stationary blade leading edge, - a movable blade (152, 252, 352, 452) having movable blade teeth forming a movable blade leading edge, wherein the movable blade (152, 252, 352, 452) and the stationary blade (134, 234, 334, 434) are arranged on top of one another and operable to be moved with respect to one another in a lateral direction, and - a guide unit (166, 266, 366, 466) formed between the movable blade (152, 252, 352, 452) and the stationary blade (134, 234, 334, 434), the movable blade (152, 252, 352, 452) and the stationary blade (134, 234, 334, 434) engaging one another at the guide unit (166, 266, 366, 466), wherein the guide unit (166, 266, 366, 466) is arranged to set a longitudinal distance (d) between the stationary blade leading edge and the movable blade leading edge and to define a movement path for the relative movement between the stationary blade (134, 234, 334, 434) and the movable blade (152, 252, 352, 452), and wherein the guide unit (166, 266, 366, 466) comprises two, longitudinally spaced, laterally extending guideways (168, 170; 268, 270; 368, 370; 468, 470), each defined between a stationary blade guide surface (172, 272) and a movable blade guide surface (174, 274) that overlap one another, wherein rolling elements (178, 180; 278, 280; 378, 380; 478, 480), preferably bearing balls, are arranged at the two guideways (168, 170; 268, 270; 368, 370; 468, 470), wherein the rolling elements (178, 180; 278, 280; 378, 380; 478, 480) are confined between the stationary blade guide surface (172, 272) and the movable blade guide surface (174, 274), wherein the stationary blade guide surface (172, 272) and the movable blade guide surface (174, 274) of each guideway (168, 170; 268, 270; 368, 370; 468, 470) have a height extension that is greater than a radius of the rolling elements (178, 180; 278, 280; 378, 380; 478, 480) at the guideway (168, 170; 268, 270; 368, 370; 468, 470), such that the at least one stationary blade guide surface (172, 272) and the at least one movable blade guide surface (174, 274) of each guideway (168, 170; 268, 270; 368, 370; 468, 470) overlap one another in a vertical direction, and wherein the stationary blade guide surfaces (172, 272) and the movable blade guide surfaces (174, 274) of the two guideways (168, 170; 268, 270; 368, 370; 468, 470) therebetween provide for a defined positive-fit coupling in the longitudinal direction between the stationary blade (134, 234, 334, 434) and the movable blade (152, 252, 352, 452) such that the guide unit (166, 266, 366, 466) provides for a set longitudinal distance (d) for any force applied in the longitudinal direction. - a stationary blade (134, 234, 334, 434) having stationary blade teeth forming a stationary blade leading edge, - a movable blade (152, 252, 352, 452) having movable blade teeth forming a movable blade leading edge, wherein the movable blade (152, 252, 352, 452) and the stationary blade (134, 234, 334, 434) are arranged on top of one another and operable to be moved with respect to one another in a lateral direction, and - a guide unit (166, 266, 366, 466) formed between the movable blade (152, 252, 352, 452) and the stationary blade (134, 234, 334, 434), the movable blade (152, 252, 352, 452) and the stationary blade (134, 234, 334, 434) engaging one another at the guide unit (166, 266, 366, 466),