The 10023400CR300 Buttweld Conical Reducer Fitting has 4.0 inch outside diameter with a reduced size 3.0 inch O.D. outlet and 0.065 in. wall thickness. This concentric reducer features high conductance conical profile to reduce the tube size over a 3.63 inch total length. Series 23 vacuum buttweld fittings are constructed with welded, drawn, and annealed 304 stainless steel tubing for applications where minimizing the number of sealed joints is critical. Stainless steel vacuum tubing offers low outgassing under vacuum conditions, is chemically resistant, annealed for consistent leak free welding, and has minimized corrosion concentration points. Series 23 fittings are designed for internal socket type welding or external buttwelding.