The details of non magnetic drill collar as follows: 1. Material: non magnetic steel 2. Shape: it is the round pipe with smooth surface and thick wall, and the both ends are machined screw thread for connection. 3. Use: it is mainly used for the inspection in the process of petroleum drilling. 4. Standard: api spec 7-1 or sy/t5144 standard. 5. Inspection&test: when producing, traceability are maintained from the receipt of raw material to completion of final products, and serial numbers are die-stamped on each workpiece body. During each manufacturing process, inspection and test are performed. 6. Magnetic permeability(mps=1¡á105/4¡ça/m) 1). Average: ur