Name:tubing couplings Std Ref: API 5CT Grade:J55,K55,N80,L80,C90 ... thread products by customer's request 3.Size: tubing coupling from 1.9" to 4-1/2 ... Our company manufacture and sell casing and tubing couplings,pup joints, tool joints, adapter pup-joints, ... couplings, stabilizers, air-liquid separators, anchors of oil pumps and revolving sand gravitated device, etc. API 5CT and 5B tubing couplings