An oblong conduit (13) for conditioning molten glass is disclosed. The wall (23) of the conduit is composed of a precious metal, e.g., a platinum-rhodium alloy, and can be equipped with precious metal tabs (29) for supporting the upper surface (25) of the wall so as to reduce sag of that surface at such times as the conduit is at an elevated temperature and is not filled with glass. The precious metal tabs (29) can be received in channels (31) formed in a refractory support structure (27). The refractory support structure (27) can be a laminate of two layers (33,35), where one of the layers (33) has a smaller grain structure than the other layer (35), the layers being held together by an adhesive (37).