A dose setting mechanism for a drug delivery device (100； 200). The mechanism may comprise a drug delivery device housing (220). A dose dial component (222) is positioned in the housing and rotatable during dose setting and dose delivery. A split threaded insert (201 ) is in threaded engagement with the dose dial component (222). The insert can transform from a first configuration to a second configuration when the dose dial component is rotated. In one dose setting mechanism arrangement, the first configuration may comprise a first open configuration and the second configuration may comprise a second closed configuration.
