A hair cutting unit (7a, 7b, 7c) for use in a shaving device, said hair cutting unit comprising: - an external cutting member (21a, 21b, 21c) having a shaving surface with hair-entry openings; - an internal cutting member which is rotatable relative to the external cutting member about an axis of rotation and which has a plurality of hair-cutting elements; - a supporting member (25a, 25b, 25c) having a skin contacting surface surrounding the external cutting member; and - a retaining component (27a, 27b, 27c) which is releasably couplable to the supporting member by means of a coupling structure (53, 55) and which is configured to retain the external cutting member in an operational position relative to the supporting member in an assembled condition of the hair cutting unit; wherein in the assembled condition: - a retained element of the external cutting member is retained between a first retaining member of the retaining component and a second retaining member of the supporting member at least in an axial direction parallel to the axis of rotation; - in a parallel orientation of the shaving surface relative to the skin contacting surface, the shaving surface protrudes relative to the skin contacting surface in the axial direction over an exposure distance; and wherein the coupling structure comprises a first guiding member provided on the supporting member and a second guiding member provided on the retaining component, the first and second guiding members being configured to: - mutually engage when the retaining component is in any angular position between a first angular position and a second angular position about the axis of rotation relative to the supporting member, the first and second angular positions being mutually different; and - establish the assembled condition in the second angular position of the retaining component; characterized in that the first and second guiding members (53, 55) are configured such that, when the first and second guiding members mutually engage in the first angular position of the retaining component (27a, 27b, 27c) resulting from manually turning the retaining component relative to the supporting member (25a, 25b, 25c) about the axis of rotation from the second angular position, i.e. the assembled condition, to the first angular position over an angular distance about the axis of rotation present between the first and second angular positions smaller than 360°, the retained element of the external cutting member (21a, 21b, 21c) is moveable between the first and second retaining members (69, 73) parallel to the axis of rotation over a distance which is at least equal to the exposure distance. - an external cutting member (21a, 21b, 21c) having a shaving surface with hair-entry openings; - an internal cutting member which is rotatable relative to the external cutting member about an axis of rotation and which has a plurality of hair-cutting elements; - a supporting member (25a, 25b, 25c) having a skin contacting surface surrounding the external cutting member; and - a retaining component (27a, 27b, 27c) which is releasably couplable to the supporting member by means of a coupling structure (53, 55) and which is configured to retain the external cutting member in an operational position relative to the supporting member in an assembled condition of the hair cutting unit; - a retained element of the external cutting member is retained between a first retaining member of the retaining component and a second retaining member of the supporting member at least in an axial direction parallel to the axis of rotation; - in a parallel orientation of the shaving surface relative to the skin contacting surface, the shaving surface protrudes relative to the skin contacting surface in the axial direction over an exposure distance; and - mutually engage when the retaining component is in any angular position between a first angular position and a second angular position about the axis of rotation relative to the supporting member, the first and second angular positions being mutually different; and - establish the assembled condition in the second angular position of the retaining component;