Provided is a cassette unit suitable for use with an auto-injector having a drive unit. The cassette unit comprises a cassette unit housing defining a cassette unit housing cavity, which is in receipt of a syringe, a rearward entrance to said cavity and a forward needle projection aperture. 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; 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; and a damping element defining a damping relationship between the cassette unit end-cap and the flange of the syringe, thereby acting to damp rearward movement of the syringe relative to the cassette unit end-cap.