Drill colllars we provide is made form 4145 H forging or rollint modified steel. Raw materials are all from top China steel group, so from the first begining, we can assure high quality. We manage our Production and Inspection Process strictly according to API SPEC 7 requirements. All the connections are phosphate- coated to improve resistance to corrision. We can also do copper plating according to clients' requirements. We offer groove, elevator groove to improve handing efficiency and safty. Slip and elevator groove are machined in complianed with API RP7G guidelines. We can also make stress relief groove according to clients' requirements. We provide free thread protector for both pin and box.

Different sizes we produce is form 3 1/2" to 11", our strength is large size like above 9" and small size like below 4 3/4".