Patent ID: 7607901

Claim:
A plunger for use in a downhole pump, comprising: a) an elongated body; b) at least portions of the body having an outside diameter that is structured and arranged to reciprocate relative to a barrel, the outside diameter having first and second ends, the outside diameter having a surface with a first hardness; c) an inner passage through the body along the length thereof; d) rings located at the first and second ends, the rings made of a second material having a second hardness, the second hardness being greater than the first hardness, the rings having an outside diameter, the ring outside diameter sized so as to produce a clearance with the barrel, the clearance providing a fluid seal; e) the plunger having a second outside diameter which is larger than the ring outside diameter, the plunger second outside diameter being made of the same material as the plunger body, the plunger second outside diameter structured and arranged to wear down to the ring outside diameter.