A stopper adapted for attachment with a plunger rod for use within a syringe barrel, the stopper comprising: a main body portion defining an open rearward end configured to receive the plunger rod, an engagement portion comprising an upwardly angled portion and a downwardly angled portion, which together form a notch with a conical cross-sectional shape extending along an inner circumference of the main body portion configured to engage at least a top portion of the plunger rod, and a closed front end forming a flexible roof, wherein the closed front end of the main body has a conical shape with a tip; wherein the closed front end of the main body portion includes a first angled portion and a second angled portion forming a single conical surface that extends toward a tip providing a closed front end and a first perimetrical skirt extending around an outer circumference of the main body portion toward the closed front end of the main body portion, wherein, when fluid pressure is increased inside the syringe barrel during an injection, the flexible roof flexes inward and expands in a radial direction toward an inner wall of the syringe barrel, the first perimetrical skirt is bent toward and forced against the inner wall of the syringe barrel, and an engagement between the plunger rod and the notch forces the wall to expand in the radial direction toward the inner wall of the syringe barrel, thereby providing a sealing pressure between the stopper and the inner wall of the syringe barrel the stopper comprising further: a second perimetrical skirt extending around an outer circumference of the main body portion toward the open rearward end of the main body portion such that the second perimetrical skirt provides stability to the stopper in an axial direction, wherein, when fluid pressure is decreased inside the syringe barrel during an aspiration, the second perimetrical skirt is forced against the inner wall of the syringe barrel, thereby providing a sealing pressure between the stopper and the inner wall of the syringe barrel. a main body portion defining an open rearward end configured to receive the plunger rod, an engagement portion comprising an upwardly angled portion and a downwardly angled portion, which together form a notch with a conical cross-sectional shape extending along an inner circumference of the main body portion configured to engage at least a top portion of the plunger rod, and a closed front end forming a flexible roof, wherein the closed front end of the main body has a conical shape with a tip; wherein the closed front end of the main body portion includes a first angled portion and a second angled portion forming a single conical surface that extends toward a tip providing a closed front end and a first perimetrical skirt extending around an outer circumference of the main body portion toward the closed front end of the main body portion, wherein, when fluid pressure is increased inside the syringe barrel during an injection, the flexible roof flexes inward and expands in a radial direction toward an inner wall of the syringe barrel, the first perimetrical skirt is bent toward and forced against the inner wall of the syringe barrel, and an engagement between the plunger rod and the notch forces the wall to expand in the radial direction toward the inner wall of the syringe barrel, thereby providing a sealing pressure between the stopper and the inner wall of the syringe barrel the stopper comprising further: a second perimetrical skirt extending around an outer circumference of the main body portion toward the open rearward end of the main body portion such that the second perimetrical skirt provides stability to the stopper in an axial direction, wherein, when fluid pressure is decreased inside the syringe barrel during an aspiration, the second perimetrical skirt is forced against the inner wall of the syringe barrel, thereby providing a sealing pressure between the stopper and the inner wall of the syringe barrel. a second perimetrical skirt extending around an outer circumference of the main body portion toward the open rearward end of the main body portion such that the second perimetrical skirt provides stability to the stopper in an axial direction, wherein, when fluid pressure is decreased inside the syringe barrel during an aspiration, the second perimetrical skirt is forced against the inner wall of the syringe barrel, thereby providing a sealing pressure between the stopper and the inner wall of the syringe barrel.