A cutting unit for a hair-cutting device, comprising: - a cutter blade with a first toothed leading edge; - a guard blade comprising: - a blade-facing surface at least engaging the cutter blade at a cut location; - a guard contact surface for contacting skin of a user; and - a substantially planar lower surface terminating at the guard contact surface and, the planar lower surface being parallel to the blade facing surface; wherein the guard contact surface and the blade-facing surface are angled with respect to each other and converge towards a second toothed leading edge with a plurality of hair-receiving slots; wherein at least one of the cutter blade and the guard blade is configured to reciprocate in a reciprocation direction such that the first toothed leading edge of the cutter blade is in a hair shearing relationship with the second toothed leading edge of the guard blade; wherein the guard blade is a longitudinally moveable blade mounted for moving in a direction perpendicular to the reciprocation direction so as to adjust a length of hairs sheared between the guard blade and the cutter blade; wherein the guard blade comprises a structure being accessible by a finger of the user to move the guard blade in the direction perpendicular to the reciprocation direction to allow a continuous adjustment of the length of hairs sheared between the guard blade and the cutter blade;; wherein the structure is located on the planar lower surface of the guard blade wherein the guard blade is presetable in a position selected from a set of predefined positions to allow a selection of different hair cutting length settings; characterized in that the guard blade is configured to return to the selected position upon release of the finger from the structure. - a cutter blade with a first toothed leading edge; - a guard blade comprising: - a blade-facing surface at least engaging the cutter blade at a cut location; - a guard contact surface for contacting skin of a user; and - a substantially planar lower surface terminating at the guard contact surface and, the planar lower surface being parallel to the blade facing surface; - a blade-facing surface at least engaging the cutter blade at a cut location; - a guard contact surface for contacting skin of a user; and - a substantially planar lower surface terminating at the guard contact surface and, the planar lower surface being parallel to the blade facing surface; wherein the guard contact surface and the blade-facing surface are angled with respect to each other and converge towards a second toothed leading edge with a plurality of hair-receiving slots; wherein at least one of the cutter blade and the guard blade is configured to reciprocate in a reciprocation direction such that the first toothed leading edge of the cutter blade is in a hair shearing relationship with the second toothed leading edge of the guard blade; wherein the guard blade is a longitudinally moveable blade mounted for moving in a direction perpendicular to the reciprocation direction so as to adjust a length of hairs sheared between the guard blade and the cutter blade; wherein the guard blade comprises a structure being accessible by a finger of the user to move the guard blade in the direction perpendicular to the reciprocation direction to allow a continuous adjustment of the length of hairs sheared between the guard blade and the cutter blade;; wherein the structure is located on the planar lower surface of the guard blade wherein the guard blade is presetable in a position selected from a set of predefined positions to allow a selection of different hair cutting length settings; characterized in that the guard blade is configured to return to the selected position upon release of the finger from the structure.