Piston rods are available in single-piece design or two-piece design depending upon the type of mud pump. For `L’ head pumps such as National and Oil Well brands, two-piece rods are offered to facilitate removal of piston. An elastic stop nut is available for tightening the piston on to the piston rod. A specially designed piston rod nut wrench is available to prevent crimping the wall of the splined elastic stop nut. Other useful piston and rod removal tools are also offered.