... /8", 2 7/8", 3 1/2", 4" ,4 1/2", 5", 5 1/2" ,6 5/82.Steel ... and surface treatment, more accurate on dimensional control MTI 400BX welder stable and reliable plus mature ... line with NS-1requirement. Proprietary product——Tool Joint 1.DPDS——Double Shoulder Tool Joint Developed by DP ... -Master's Advantages Strategic partnership with Tuboscope 1)Quality Control-Tuboscope Inspection on all New Drill Pipes ...