the cartridge comprises a liner which is fastened at its outlet end to an outlet assembly which in turn is attachable to the front piece of the cartridge and which is held at its inlet end thus , that the piston slides inside the liner package . at the inlet end the liner is either fastened to the piston or to a ring insertable into the inlet end of the cartridge . such a liner package has a low volume and plastic waste to be disposed of whereas the cylinders and the front piece of the cartridge are re - usable , whilst all performances of a rigid cartridge can be maintained or surpassed .