The coupling is an oilfield drilling tools, mainly for tubing and casing connection, so there are mainly two types, one is tubing coupling another is casing coupling .The connection we can provide including API standard and non-API standard，steel grade namely J55 、K55、 N80、 L80、 C90、 T95、 P110. Furthermore we can provide the premium connection such as DL-V series, DL-J series, DL-H series, and DL-T series, which have the same performance with Vam series, JFE series, Hunting series, Tenaris-Hydril series.