A bone filler delivery device includes a syringe assembly. The syringe assembly has a barrel with a first opening for dispensing bone filler and a second opening adapted to receive a plunger. A plunger is adapted to mate with the barrel to define a bone filler dispensing chamber therein. The plunger can move through the barrel in an axial direction. A seal is coupled to the plunger and is adapted to seal against the barrel. The seal includes an annular body and an annular first lip that extends from the body in a first direction and is adapted to flex toward the barrel when the plunger is moved through the barrel toward the first opening.