Described herein is an actuator housing (500) for use with a metered dose inhaler (MDI) device which comprises a housing portion (115) having a nozzle block in which an actuator seat and an actuator nozzle are formed, and a mouthpiece portion (525) joined to the housing portion (115). The mouthpiece portion (525) has an external surface having a first or guidance region (570) over which teeth of a patient are to be located and a second or sealing region (580) against which lips of the patient seal during dispensing of a medicament. In one embodiment, the first or guidance region (570) comprises a plurality of longitudinally extending flutes arranged around the external surface and located adjacent to a mouthpiece end face (560). An optional annular projection (590) may be provided to define more precisely the sealing region for the patient.
