Injection device for injecting a highly viscous medium, comprising a syringe for injecting a highly viscous medium having a syringe body and a piston rod assembly and a needle assembly comprising a needle hub and a cannula, wherein the syringe body comprises a distal end portion and a proximal end portion, wherein the syringe body is hollow cylindrical and forms a chamber for receiving the highly viscous medium, wherein the proximal end portion comprises an opening through which a piston rod assembly is insertable into the chamber, wherein the piston rod assembly comprises a piston rod and a piston attached to a distal end of the piston rod, wherein the piston is received in and displaceably guided within said chamber via said opening at the proximal end portion of the syringe body, wherein a Luer lock connector is formed at the distal end portion of the syringe body, which connector comprises an outer cone having a further opening for dispensing the highly viscous medium and a sleeve-shaped portion comprising an internal thread, wherein the needle hub comprises a Luer lock connector counterpart complementary to the Luer lock connector of the syringe body for establishing a Luer lock connection between the syringe body and the needle assembly, and wherein for a Luer lock connection of the Luer lock connector with the Luer lock connector counterpart the syringe body has a minimum NPO resistance between 90 N and 105 N, as measured according to the method specified in the description on pages 3 to 5, wherein the syringe body at the proximal end portion comprises an inner peripheral surface having a chamfer which causes the inner peripheral surface to taper as viewed from the proximal end portion in the direction of the distal end portion, characterized in that, the chamfer as viewed in the direction of a longitudinal axis of the syringe body has a length (w) between 1.2 mm and 1.8 mm, preferably from 1.4 mm to 1.6 mm, more preferably of 1.5 mm, and/or wherein the chamfer forms an angle (y) of at least 13°, preferably at least 14°, more preferably at least 15°, with the longitudinal axis. wherein the syringe body comprises a distal end portion and a proximal end portion, wherein the syringe body is hollow cylindrical and forms a chamber for receiving the highly viscous medium, wherein the proximal end portion comprises an opening through which a piston rod assembly is insertable into the chamber, wherein the piston rod assembly comprises a piston rod and a piston attached to a distal end of the piston rod, wherein the piston is received in and displaceably guided within said chamber via said opening at the proximal end portion of the syringe body, wherein a Luer lock connector is formed at the distal end portion of the syringe body, which connector comprises an outer cone having a further opening for dispensing the highly viscous medium and a sleeve-shaped portion comprising an internal thread, wherein the needle hub comprises a Luer lock connector counterpart complementary to the Luer lock connector of the syringe body for establishing a Luer lock connection between the syringe body and the needle assembly, and wherein for a Luer lock connection of the Luer lock connector with the Luer lock connector counterpart the syringe body has a minimum NPO resistance between 90 N and 105 N, as measured according to the method specified in the description on pages 3 to 5, wherein the syringe body at the proximal end portion comprises an inner peripheral surface having a chamfer which causes the inner peripheral surface to taper as viewed from the proximal end portion in the direction of the distal end portion, characterized in that, the chamfer as viewed in the direction of a longitudinal axis of the syringe body has a length (w) between 1.2 mm and 1.8 mm, preferably from 1.4 mm to 1.6 mm, more preferably of 1.5 mm, and/or wherein the chamfer forms an angle (y) of at least 13°, preferably at least 14°, more preferably at least 15°, with the longitudinal axis.