A drug delivery device comprising a display assembly, the display assembly comprising - a body defining a window having an axial extension, - an indication member for providing information to be displayed in the window, wherein the indication member is movable relative to the body for changing the information displayed in the window, - a selection member, wherein - the selection member defines a masking section and a non-masking section, - the selection member is rotatable around a rotation axis (x) with respect to the body and with respect to the indication member, - the non-masking section and the masking section partially overlap with the window to define a displayed section of the indication member, wherein the indication member is an indication sleeve and the selection member is a selection sleeve, wherein the indication sleeve is retained in the selection sleeve, characterised in that the selection member and the indication member are coupled such that: a) movement of the indication member with respect to the body is converted into rotational movement of the selection member with respect to the indication member and the displayed section of the indication member is axially displaced within the window or b) rotational movement of the selection member with respect to the body is converted into movement of the indication member with respect to the selection member and the displayed section of the indication member is axially displaced within the window, wherein the selection member and the indication member are coupled by a coupling member, wherein the coupling member defines a coupling member window, the displayed section of the indication member being displayed through the coupling member window and the window, wherein the coupling member is threadedly coupled to the indication member, axially guided with respect to the body and guided along the non-masking section of the selection member, wherein the indication member is axially constrained but rotatable relative to the body, wherein the selection member is axially constrained relative to the body, wherein the body is a housing of the drug delivery device, wherein the display assembly provides a dose display mechanism to display the size of the dose which is set to be dispensed by the drug delivery device to a user through the window, and wherein the drug delivery device further comprises: i) a piston rod; and/or ii) a cap covering a distal end of the drug delivery device. - a body defining a window having an axial extension, - an indication member for providing information to be displayed in the window, wherein the indication member is movable relative to the body for changing the information displayed in the window, - a selection member, wherein - the selection member defines a masking section and a non-masking section, - the selection member is rotatable around a rotation axis (x) with respect to the body and with respect to the indication member, - the non-masking section and the masking section partially overlap with the window to define a displayed section of the indication member, - the selection member defines a masking section and a non-masking section, - the selection member is rotatable around a rotation axis (x) with respect to the body and with respect to the indication member, - the non-masking section and the masking section partially overlap with the window to define a displayed section of the indication member, a) movement of the indication member with respect to the body is converted into rotational movement of the selection member with respect to the indication member and the displayed section of the indication member is axially displaced within the window or b) rotational movement of the selection member with respect to the body is converted into movement of the indication member with respect to the selection member and the displayed section of the indication member is axially displaced within the window, i) a piston rod; and/or ii) a cap covering a distal end of the drug delivery device.