Waterco MTJ-770-S Tool, Socket, System3 3" Knob, Stainless SteelModel MTJ-770-S "System 3" Clamp Socket This socket may be used with a 3/8"-drive socket wrench or any portable drill or driver. This metal version of MTJ-770 socket FITS ONLY THE 3" CLAMP KNOBS USED ON PENTAIR LATER MODEL SYSTEM 3 FILTERS. Insert a flat-tip screwdriver between each clamp assembly and the filter tank prior to removal of the knob. As the knob loosens, pry the entire clamp assembly away from the tank wall so that both knob and assembly are removed together. Otherwise, the knob will come away from the assembly with possible loss of the knob 'C' clamp or washer and failure to remove clamp assembly from the filter tank will occur.