API Tubing Coupling 1) Standard: API 5CT. 2) Material: J55, K55, L80, N80 ... NUE EUE 4) Inside Phosphate T API external-upset tubing coupling Dimensions, tolerances and massesLabel 1SizeaOutside diameterMinimum lengthmmDiameter of recessmmWidth of bearing regularmmMaximum ... coupling is used;b. Tolerance on outside diameter W, ± 1 %;c Tolerance on outside diameter Wc, ± 0,38 mm. j55 petroleum tubing and ...