I understood that there are 2 types of leakless pumps. One has stops so that the thrust is not dependent on the stop in the head. Also, one has the bearing that does not require any lubrication as stated above, the other has a greaseless bearing on both ends and therefore does not require and lubrication at all. The OP wanted to know how to tell the difference between the farious types including the originals. So far that is not answered here. Jack