A dose setting mechanism for a medicament delivery device includes a tubular housing having threads on its inner surface, a first window, a second window, and at least one surface opening; a tubular dose limiting member having a first thread segment on its outer circumference for the threads on the housing's inner surface, first indicia on its outer circumference, a stop surface, and equidistant protrusions on its outer circumference; a tubular dose setting member; and a removable lock member attached to the housing. The housing is coaxially arranged inside the dose limiting member and includes a second thread segment for the housing's threads, second indicia, and a dose setting knob protruding through the housing. The lock member includes at least one elongated rib on its inner circumferential surface for interacting with the protrusions for locking the dose limiting member in position when the lock member is attached to the housing.