The present disclosure is generally directed to a drug delivery device for selecting and dispensing a number of user variable doses of a medicament. The device comprises a housing (10), a dose selector (80) operable to set a dose by rotation relative to the housing (10), a number sleeve (60) arranged within the housing (10) such that at least a portion of the number sleeve (60) is visible through a first aperture (11b) in the housing (10), a piston rod (30) coupled to the housing (10) and to a drive sleeve (40) such that rotation of the drive sleeve (40) relative to the housing (10) causes the piston rod (30) to translate relative to the housing (10) and a clutch mechanism arranged between the number sleeve (60) and the drive sleeve (40). The clutch mechanism comprises a first interface (42, 62) for rotationally constraining the drive sleeve (40) and the number sleeve (60) depending on the axial position of the drive sleeve (40) and a second interface (43, 121) for rotationally constraining the drive sleeve (40) and the number sleeve (60) via a clutch element (120) depending on the axial position of the drive sleeve (40) and/or the bias of a clutch spring (130).
