We Haixin Group locals SINOPEC ( 2nd largest) shengli oil field In China, YM : sukkersu at yahoo com ,have one manufacturer base of Drill pipe with API 5D Certificaiton, and one trading branch which supply Drill collar, Non-magnetic collar, Spiral Drill Collar, according API 7 standard. Material of 4145H, OD: 3 1/ 8" to 10" ; Length 30' / 31' ;