Abstract: A plug comprises a refractory body having a plurality of gas passgeways through which gas is blown into a refining apparatus. Each gas passageway may be defined by at least two metal tubes which are longitudinally spaced apart from each other. Alternatively, each gas passageway may be at least partly defined by an electrically insulating tube. The plug may alternatively have a plurality of gas passageways each having a bare refractory wall, while the body is reinforced with nonconductive mineral fibers, or metal wires which do not continuously extend throughout the plug. The plug may further be provided with a plurality of elongated holes extending in parallel to the gas passgeways from the inner surface of the body facing the interior of the refining apparatus to an intermediate portion thereof.