These devices are designed to assist sewer cleaning hose through tight corners and around bends.  They disable one of the inlet valves (on a triplex pump), which adds pulsation to the downstream hose and nozzle.  This extra pulsation then allows the operator to move the hose further downstream.  They can be installed on nearly all types of pumps including P200, P300, P400, MP Series, LP Series and GP Series pumps.