| CPC F04B 47/12 (2013.01) [E21B 43/121 (2013.01); F04B 53/00 (2013.01)] | 15 Claims |

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1. A plunger, the plunger comprising:
a plunger body having a radially directed flow hole disposed therein;
a pin that is removable from the plunger body, the pin shifts back and forth in the plunger body to block the flow hole in a first position and allow fluid to flow through the flow hole in a second position;
a clutch mechanism supported by the pin to control the force necessary to shift the pin in the plunger body; and
a bumper portion supported by a body of the pin to limit the travel of the pin in the plunger body during operational use of the plunger, the bumper portion includes a bumper sleeve disposed on a neck portion of the pin.
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