API Non-Upset Tubing Coupling - Dimensions, Tolerances and Masses
Size Designation
Pipe
Outside Diameter
Coupling Minimum Length Diameter of
Recess
Width of
Bearing Face
b
Maximum
Bearing Face
Diameter,
Special Bevel 
Mass
Outside Diameter
D (in) D (in) W (in) N˪ (in) Q (in) (in) Bƒ (in) (lb)
2-3/8 2.375 2.875 4  1/4 2.438 3/16 2.625 2.82
2-7/8 2.875 3.500 5  1/8 2.938 3/16 3.188 5.15
 
3-1/2 3.500 4.250 5  5/8 3.563 3/16 3.875 8.17
4 4.000 4.750 5  3/4 4.063 3/16 4.375 9.58
4-1/2 4.500 5.200 6  1/8 4.563 3/16 4.850 10.77
Refer Figure 4
The size designation for the Coupling is the same as the size designation for the Pipe on which the Coupling is used.
Tolerance on Outside Diameter W: ± 1 %