A breath-responsive metered dose inhaler having a trigger mechanism for triggering delivery of a medicament and a trigger mechanism chassis for locating the trigger mechanism within the inhaler, the trigger mechanism including a breath responsive member moveable upon inhalation of the user from a primed position in which the inhaler is prevented from delivering medicament, to a triggered position in which the medicament is delivered to the user, a spring which is flexible along its longitudinal axis, wherein the spring is configured to bias the breath responsive member from its triggered position to its primed position by flexure along its longitudinal axis.
