... ,carbon steel,stainless steel etc. Drill collars is one of the most important product which mainly used to provide bit weight ... collars are manufactured strictly from API Spec7-1 standard. The product quality and stability, the customers satisfaction is 100%. For more than 40 ... Pipe, Drill Collar, Heavy Weight Drill Pipe, Kelly,Pup Joint and so on. (Factory)API 7-1 Spiral Drill Collar--Drilling tool