A vial cap for sealing the open end of a vial and allowing easy access to a hypodermic needle or pipette to withdraw or add fluid or liquid into or from the vial. The lid consists of a flange connected to a cylindrical body with an internal truncated cone shape ending in a flexible circular flap hinged to the perimeter of the cone section, and that the needle can bend aside, and upon withdrawal of the needle return to a sealing position against the truncated cone. The outer cylindrical body has a band portion to provide an friction interference fit against the internal surface of the vial. The outer cylindrical wall has a taper to aid insertion. The vial lid forms part of a robotic fluid transfer system. The cap is made from polyethylene elastomer.
