Size range of casing and tubing couplings of Teda Special Pipe Co Ltd:4 1/2"~20". Teda Special Pipe Co Ltd produces Casing & Tubing coupling according to API 5CT Spec. The steel grade of material we use:H40,J55,K55,M65,N80,L80,C90,T95,P110,Q125. Size range of casing and tubing couplings of Teda Special Pipe Co Ltd:4 1/2"~20". Long and Short Round Thread Casing Coupling Nom SizeODOutside DiaMin ...