Tube OD ( mm )6 10 14 18 22 28 34 42 50 DN( mm) 4 6 7 10 11 12 13 15 17 20 22 25 28 32 40 NPTRG 1/8 1/8 1/4 3/8 1/2 3/4 1 11/4 11/2 1/4 3/8 1/2 3/4 1 11/4 11/2 Metric D M10x1 M10x1 M14x1.5 M18x1.5 M22x1.5 M27x2 M33x2 M42x2 M18x2 M14x1.5 M18x1.5 M22x1.5 M27x2 M33x2 M42x2 M48x2 Used tube Thread: M12x1.25 M16x1.5 M22x1.5 M27x1.5 M30x1.5 M36x2 M42x2 M52x2 M60x2 Model sample:the welded tube OD is ?28 ,terminal thread is R1,the weld coupling with taper thread is marked :Q/ZB204-77R1"?28