Syringe with high pull-out resistance

A syringe comprising:

• a syringe body for receiving a product for injection, the syringe body comprising a stopper, the stopper having an inner wall and delimiting a cavity, the inner wall being elastically deformable;
• a piston mounted so as to be able to slide inside the syringe body in an injection direction of the product and in an other direction opposite to the injection direction of the product, the piston comprising a rod having a first end and a second end opposite the first end;
• a pusher at the first end of the rod;
• and
• a snap-fastening head at the second end of the rod and snap-fastened inside the cavity of the stopper, the snap-fastening head having a planar bearing surface bearing against the inner wall of the stopper when the piston slides in the other direction that is opposite to the injection direction of the product;
• wherein the snap-fastening head comprises at least one protruding element that protrudes from the planar bearing surface and that is arranged so as to penetrate the inner wall of the stopper when the piston slides in the other direction that is opposite to the injection direction of the product so that the at least one protruding element is anchored to the inner wall by locally deforming the inner wall;
• wherein the planar bearing surface has a radius (R), and the at least one protruding element has a lateral end situated at a radial distance (r), such that:
• 0.8 R≤r≤1.20 R.