Disclosed herein are fastening features for cartridge assemblies that include coding features that help dedicate a medicament reservoir to specific injection devices. An exemplary cartridge assembly comprises a cylindrical inner surface for holding medicament and a cylindrical outer surface comprising a fastening feature having a first coding element protruding from the cylindrical outer surface. The coding element is configured to engage a complementary coding feature on the fastener on a dose setting member specifically configured to dispense the medicament, thereby allowing only the correct cartridge assembly to connect to the correct dose setting member.