a valve which can be used to facilitate needleless transfer of medication from the container to a patient . a slidable actuator is engaged by the nozzle portion of a syringe and the tapered lead portion of the slide is forced into the container through a pre - slit elastomeric membrane . the membrane is relatively thick , preferably between 25 and 75 % the width dimension of the membrane and , more preferably , between 40 and 50 % of that dimension . the thick membrane is durable enough to withstand repeated usage and damage resistant enough to permit use with needled syringes .