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).
