它是个上端为钻杆母扣或者由壬，下端为套管公扣，内空心的转换接头。
Its upper end is drill pipe box or union, the nether end is casing pin. It is a crossover with hollow inside.
它由公扣和母扣组成，公扣的外周设有安装环槽，公扣的一端设有凸出部；
The periphery of the male buckle is provided with an installing ring groove, and one end of the male buckle is provided with the bulge.
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