The present invention is directed to a pen-type injector equipped with a cartridge holder (1) for a drug delivery device. The cartridge holder has a longitudinal axis and comprises a body (5) for receiving a cartridge, wherein the body (5) comprises at a proximal end (6) engagement means (8) for releasably coupling the cartridge holder (1) to the drug delivery device (2, 3), a latch member (11) for releasably engaging a cap (4) of the drug delivery device and an alignment element (11; 14) which is visual from the outer side of the body (5). The alignment element may be an aperture (14) provided in the body (5) and/or a lug (11) which forms the latch member.