I pitched the stock stopper and used an extra Sulivan I had in the pile, along with the Sullivan plastic back plate. It all stacks up like so.....stock metal front plate(hole drilled out to accept the Sullivan screw)/Sullivan stopper/stock metal back plate(hole drilled too)/Sullivan plastic back plate. The Sullivan stopper is a loose fit in the stock tank but with enough turns the stopper will mushroom enough to fill and seal the gap. The reason for the metal parts is so that I can really crank down on the screw and compress the stopper well. The Sullivan plastic back plate will not allow the screw to loosen up at all.