A bi-directional electrostatic discharge diode structure consumes substantially less silicon real estate and provides ultra-low capacitance by utilizing a p\u2212 epitaxial layer that touches and lies between an n+ lower epitaxial layer and an n+ upper epitaxial layer. Each series resonant output circuit is used to drive two gas discharge lamps. The method further includes dispensing in a flow having a first direction a slurry onto a substrate, wherein the slurry includes a fluid. In use, a child squares the hub on the first face and cones the hub on the second face with sandpaper. When the level sensor probes are in the upward position they touch electrical contacts completing a self-test circuit confirming electrical continuity through the level sensor probes. The invention provides that the adjustment ring protrudes forwards in an axial direction beyond an axially rear end of the tool clamping unit, at least when the tool clamping unit is completely open.