1. Cangzhou Zhongxing Petroleum Equipment Co
Ltd.
2. Challenger International Inc.
3. DP-Master Manufacturing (S) Pte Ltd.
4. Drill Pipe International
LLC
5. Hilong Group of Companies
6. Hunting PLC
7. International Drilling Services Ltd.
8. NOV Inc.
9. Oil Country Tubular Limited.
10. Tejas Tubular Products Inc.
11. Tenaris S.A.
12. Texas Steel Conversion Inc.
13. TMK Group
14. Weatherock Group Holding Limited
15. Workstrings International