Cangzhou Shengdali Machinery Manufacture Co. Ltd is a professional oil production tubing, casing coupling manufacturers. Casing collar28 specifications, a total of 10 kinds of steel grade. The main types of long  round thread (LC), the short round thread (STC), buttress  thread casing(BC). Special-bevel couplings have non-upset tubing(NU) and extend-upset tubing EU. two, sealing ring with a collar, reducing coupling, and the special combination of coupling space coupling biased trapezoidal screw casing and plus Two thick tubing. ,