A method for producing polymers with controlled molecular weight and desired end functionalities and the resulting polymers. Force acting on the tappet from a plunger due to fuel pressure is dispersed to a sliding contact surface outside the hollow so that contact face pressure between the tappet and the cam ring is smaller. The lip has a plurality of circumferentially spaced passages that extend through the lip for venting air during compression molding of the liner. for use in biomedical electrodes.