Smoother, to be used in combination with mixing nozzle extension for deeper bonding with injection anchors. One side of the mixing nozzle extension is placed on the mixing nozzle of the injection anchor, on the other side the piston plug/float is attached. When the borehole is filled with mortar from below, the float will float on the injected mortar and thus prevent air entrapment in the mortar. The # number of the piston plug/float corresponds to the drill diameter.