A person having diabetes will often be required to take both slow acting and fast acting forms of insulin. It is important to be able to distinguish readily between medicament cartridges containing different medicaments. The present invention enables more ready distinction as between medicament cartridges containing different medicaments. An adaptor top for a medicament cartridge, the medicament cartridge comprising a cylinder having a main body portion, a neck portion at a first end having a radially outwardly directed flange portion, a narrowing shoulder portion connecting the body portion and the neck portion, a cap beaded across the first end thereby to retain a fluid impermeable membrane, and the adaptor top comprising a first cylindrical body portion having a radially inwardly directed flange at one end, in use to be seated over and against the cap and a second cylindrical skirt portion being adapted, in use, to be seated against the shoulder portion of the cartridge, the second skirt portion including a plurality of fingers, the free ends of the fingers in use being adapted to be seated beneath the outwardly directed flange of the medicament cartridge.