An actuator for an inhaler, in particular a nasal actuator, is disclosed, the actuator comprising a body, a stem post and fixing means for fixing the stem post in the body. The body comprises a delivery passage for delivery of a medicament and a canister opening for insertion of a canister having a metering valve with a valve stem. The stem post comprises a stem socket for receiving the valve stem of a canister and comprises an orifice for discharging a medicament to the delivery passage. The stem post and body are adapted so they cooperate to define a transition chamber when the stem post is fixed in the body. Also disclosed is a method of forming an component for an actuator for an inhaler, and a method of assembling an actuator for an inhaler by inserting the stem post through the canister opening and into the body thereby.