API Couplings are short pieces of casing or tubing used as a kind of connection between the individual joints. They are normally made of the same grade of steel as the casing or tubing. 
Many customers require the color coating on the couplings before shipment. In this way, they can easily differ the pipes after the discharge in the port.
There are different steel grades for couplings, which are identified by various colors like: 
J55 / K55-Bright Green
P110-White 
N80 / L80-Red
For the same colored couplings, we can tell the steel grade according to the color of the belt. 
Descriptions: 
1 Standard: API 5CT/ 5B
2 Steel Grade: H40、J55、K55、N80-1、N80Q、L80、P110
3 Tubing Coupling: 
OD: 2-3/8’’, 2-7/8’’, 3-1/2’’, 4’’, 4-1/2’’
Threads: NUE--Non Upset 
        EUE---External Upset
4 Casing Coupling:
OD: 4-1/2’’, 5’’, 5-1/2’’, 6-5/8’’, 7’’, 7-5/8’’, 8-5/8’’, 9-5/8’’, 10-3/4’’, 11-3/4’’, 13-3/8’’, 16’’, 18-5/8’’, 20’’
Threads: STC, LTC, BTC
We accept small quantity order and samples are also available. Quality can be checked before order confirmation. Apart from Couplings, Borun also manufacture and supply other OCTG products such as Seamless Casing Pipe, ERW Casing, Oil Tube, API Pup Joints., Drilling Pipe etc.