A cassette unit for use with an auto-injector having a drive unit, said cassette unit comprising: a cassette unit housing defining a cassette unit housing cavity, a rearward entrance to said cavity and a forward needle projection aperture; said cassette unit housing cavity in receipt of a syringe comprising: a barrel for containing a volume of a liquid drug formulation, said barrel defining a flange at the rear end thereof and a forward shoulder at the forward end thereof; a hollow needle at a front end of said barrel, said hollow needle defining a needle tip for dispensing of said liquid drug formulation; and a plunger that is axially movable within the barrel; in capping relationship with said 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 the flange of the syringe, 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, characterized in that the biasing element and the damping element are comprised as a unitary biasing and damping element (45; 145; 245; 345; 445; 545; 645; 745), and wherein the biasing and damping element is provided with one or more damping projections (47; 147; 247; 347; 447; 547; 647; 747) that project forwards towards the flange of the syringe. a cassette unit housing defining a cassette unit housing cavity, a rearward entrance to said cavity and a forward needle projection aperture; said cassette unit housing cavity in receipt of a syringe comprising: a barrel for containing a volume of a liquid drug formulation, said barrel defining a flange at the rear end thereof and a forward shoulder at the forward end thereof; a hollow needle at a front end of said barrel, said hollow needle defining a needle tip for dispensing of said liquid drug formulation; and a plunger that is axially movable within the barrel; a barrel for containing a volume of a liquid drug formulation, said barrel defining a flange at the rear end thereof and a forward shoulder at the forward end thereof; a hollow needle at a front end of said barrel, said hollow needle defining a needle tip for dispensing of said liquid drug formulation; and a plunger that is axially movable within the barrel; in capping relationship with said 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 the flange of the syringe, 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, characterized in that the biasing element and the damping element are comprised as a unitary biasing and damping element (45; 145; 245; 345; 445; 545; 645; 745), and wherein the biasing and damping element is provided with one or more damping projections (47; 147; 247; 347; 447; 547; 647; 747) that project forwards towards the flange of the syringe.