34 of the insulating tube 32 as those skilled in the art will readily appreciate minimizing the contact area between the tube 32 and the inner wall 42 minimizes heat transfer between the airfoil portion 18 and the insulating tube 32 as shown in fig4 the shroud 30 preferably has a u201c z notch u201d configuration of the type known in the art each shroud 30 includes at least one and preferably a plurality of cooling passages 44 each cooling passage 44 has a cooling fluid outlet 46 adjacent an edge 48 that forms a portion of the z notch each cooling passage 44 communicates with an inlet 24 through one of the tubes 32 as shown in fig5 each shroud 30 has a radially inward facing surface 50 a radially outward facing surface 52 and a shroud edge 48 extending therebetween each cooling passage 44 is located between the radially inward facing surface 50 and the radially outward facing surface 52 the cooling passages 44 are approximately parallel to the radially inward facing surface 50 each tube 32 has a second end 54 radially outward from the first end 38 thereof the second end 54 abuts a tube retention plug 56 the tube retention plug 56 has an internal flowpath 58 including a flowpath inlet 59 and at least one flowpath outlet 60 the second end 54 of the tube 32 is preferably sealingly fixed to the tube retention plug 56 at the flowpath inlet 59 each cooling passage 44 is in fluid communication with one of the tubes 32 through.