Single and multi-probe slide screw impedance tuners incorporate DC bias networks. Also a protrusion can be attached to the body portion at the vertex of the wedge shaped cross section, wherein said protrusion forms a notch allowing said protrusion to be secured against a sheet. compounds which modify the association of creatine kinase with other cellular components. Test voltage is controlled to avoid resistor damage. The structure reduces the weight and number of parts required to support accessories.