API Tubing Coupling 1) Standard: API 5CT. 2) Material: J55, K55, L80, ... ) Type: NUE EUE 4) Inside Phosphate T API external-upset tubing coupling Dimensions, tolerances and massesLabel 1SizeaOutside diameterMinimum lengthmmDiameter of recessmmWidth ... Tolerance on outside diameter Wc, ± 0,38 mm. j55 petroleum tubing and casing