cut at one or more convenient locations whereupon fittings as shown in fig4 can be installed to reunite the cut ends referring to fig4 the fitting includes a component part 60 provided at one of its ends with a counterbore 61 for receiving the end 62 of a first section of metal tubing the design of the counterbore 61 and adjacent portions of the fitting part 60 will be recognized as intended for welding the fitting to the tubing obviously any other suitable method of joining the fitting part 60 to the tube end 62 may be utilized additional means consisting of the metallic sleeve 63 is provided for attachment to an end 64 of another section of metal tubing in this example the end of sleeve 63 is provided with a counterbore 65 for receiving the tube end 64 and for welding thereto in manner similar to that of tube end 62 in counterbore 61 the sleeve 63 is disposed with a loose sliding fit within a bore 26 passing through the component part 60 as seen in fig4 the outside of said sleeve 63 is provided with a circumferential groove 27 confronting a circumferential groove 28 on the inside of the bore 26 a staking or retention wire.