The present invention relates an elongated housing for an injection device (10) for delivery of a liquid medicament, the housing comprising: - a tubular-shaped cartridge holder (20) to accommodate a cartridge (50) filled with the medicament and comprising a proximal connecting end (21), - a body (30) to accommodate a drive mechanism (5) operably engageable with a piston (52) of the cartridge (50), wherein the body (30) comprises a distal connecting end (31) connectable to the proximal connecting end (21), - wherein one of the proximal connecting end (21) and the distal connecting end (31) comprises an insert section (22), - wherein the other one of the proximal connecting end (21) and the distal connecting end (31) comprises a receptacle (32) to axially receive the insert section (21), - wherein the insert section (22) comprises at least one fastening element (25) to positively engage with a complementary-shaped fastening element (35) of the receptacle (32) to provide an axial interlock (6) of the cartridge holder (20) and the body (30), - wherein the fastening elements (25, 35) of the insert section (22) and the receptacle (32) comprise at least one pair of a radial protrusion (135) mating with a radial recess (125) provided on an inside wall (36) of the receptacle (32) and on an outside wall (26) of the insert section (22) and - wherein a radial depth (D) of the radial recess (125) is smaller than a thickness of the sidewall of the insert section (22) or a thickness of a sidewall (33) of the receptacle (32).
