In an effort to make the cartridge easier to use we have removed a part from the cartridge itself.
The plastic arm that used to stick out of the cartridge has been removed, and replaced by this yellow plastic clip.
The clip actually attaches to the back of the printer carriage (where the cartridges are inserted).
Once this yellow part is clipped into position the actual cartridges are installed as normal. Also once the yellow clip is in position it does not need to be removed when you use another compatible cartridge.