The Vinmetrica Electrode Holder attaches to the Lab Support Stand and has an easy to turn thumb screw for positioning the electrode to just where you need it. We recommend pressing the electrode gently down while it is held by the holder, this insures it is properly secured. Designed for a 3/8 in. pole. The Electrode holder can hold either electrode which is great when using the SC-100A, SC-200 and the SC-300 analyzers.