1.OD:2 3/8"-6 5/8" 2.Grade:E,X,G,S ... are machined by CNC Lathes and inspected with API Spec standard thread gauges. To improve the ... are produced in accordance to Standards of API 5DP, API7 &7-1, NS-1. RUSSIA RTN, RUSSIA ... GOST-R, ISO 9001,ISO 14001, OHSAS 18001, Arnco Hardbanding Certificates and so on. 2 ... 3/8--5 1/2 drill pipe