A cartridge assembly (200) having a shared fastening features for use with a drug delivery device (202). The cartridge assembly includes a cartridge holder (204), a drug cartridge (206), and a connector (208). The connector may be attached to the drug cartridge. The cartridge assembly further includes a fastening means (210, 212) for fastening to a drug delivery device, and this fastening means is shared between the cartridge holder and the cartridge or between the cartridge holder and the connector. The drug delivery device may be a reusable drug delivery device or a disposable drug delivery device.