... delivery 4.Alloy steel,carbon steel,stainless steel etc. Drill collars is one of the most important product which mainly used ... centralized and hole track by large rigidity. BSD brand drill collars are manufactured strictly from API Spec7-1 standard. The ... developing upon producing various oil drilling tools including Drill Pipe, Drill Collar, Heavy Weight Drill Pipe, Kelly,Pup Joint and so on. ...