A method and apparatus is provided for reducing the purge volume of a well during purging and sampling operations. or more ) and a radical generating agent, wherein the compounding ratio of the component, the component and the radical generating agent, based on the total weight thereof, is: 1 to 98. The surfaces to be bonded are polished to a high degree of smoothness and planarity. The piston and clutch housing assembly are configured such that only a small portion of the expandable chamber is pressurized when the piston is in the disengaged position, thereby providing improved response time for movement of the piston to the engaged position. The pin members have a splined head adapted to be engaged with a splined driver secured to an installation tool. The polystyrene resin is a copolymer comprising a styrene monomer and a acrylate monomer.