an automatic lubrication assembly that dispenses grease under pressure to machinery which requires frequent lubrication , including a spring biased one - piece rigid plastic molded plunger that has a flexible thin walled sealing lip eliminating the requirement for any seals , slidable in an open ended plastic grease cup covered by a removable cap that permits the biasing spring to be easily changed . the grease cup is formed integrally with a plastic base that has a metal outlet fitting insert molded therein that extends into the cup a substantial distance beyond a transverely positioned inlet fitting in the base to absorb side loads on the plastic cup and base .