The present invention relates to a dose setting mechanism intended to be used in a medicament delivery device, comprising an elongated tubular distal housing (16) having opposite distal and proximal ends, wherein said distal housing comprises threads (14) on its inner surface, a first window (30), a second window (32), and at least one opening (38) on its elongated surface a tubular dose limiting member (10) having opposite distal and proximal ends, wherein said dose limiting member comprises a first thread segment (12) on its outer circumference surface at its proximal end intended to cooperate with corresponding threads on the inner surface of the distal housing, first indicia (18) on its outer circumferential surface, a stop surface (42) at its proximal end, and a number of protrusions (20) arranged equidistant to each other along the circumference on the outer surface at its distal end a tubular dose setting member (22) having opposite distal and proximal ends, wherein said distal housing is coaxial-ly arranged inside the dose Hmiting member and comprises a second thread segment (24) having and end surface (44) on its outer circumferential surface at its proximal end intended to cooperate with the threads of the distal housing, second indicia (26) on its outer circumferential, and a dose setting knob (28) protruding through the distal end of the distal housing and a removable lock member (36) attached to the distal housing, wherein said lock member comprises at least one elongated rib (40) on its inner circumferential surface which is intended to interact with the protrusions of the dose limiting member for locking the dose limiting member in a certain position when the lock member is attached to the distal housing.
