Provided is a cassette unit suitable for use with an auto-injector having an electrically powered drive unit. The cassette unit comprises a cassette unit housing defining a cassette unit housing cavity, a rearward entrance to said cavity and a forward needle projection aperture. The housing cavity may receive a syringe comprising a barrel a needle at a front end of the barrel and a plunger that is axially movable within the barrel. The cassette unit also comprises in capping relationship with the rearward entrance of the cassette unit housing, a cassette unit end-cap, said cassette unit end-cap defining a drive rod-receiving opening for receipt of a drive rod for providing forward axial drive to said plunger and a biasing element defining a biasing relationship between the cassette unit end-cap and an end flange of the syringe barrel, thereby urging the syringe forwards in relation to the cassette unit end cap.
