A syringe plunger/jacket assembly may comprise a flexible jacket attached to a rigid plunger. The jacket may comprise at least two sealing rings (front and rear) that prevent fluid from leaking out of the rear of the barrel during injection of fluid from the syringe. The rear sealing ring may or may...http://www.google.ca/patents/US7819845?utm_source=gb-gplus-sharePatent US7819845 - Syringe plunger jacket with expandable seal
