All the 5" drill pipes (G-105 or S-135) are made in according to API Spec7, RP7G and API5D. We purchase the mother pipe in home and abroad, and the mother pipes are manufacutred in according to API5D and posesses the 5D Cert. The tool joints are made from AISI 4137 alloy steel and meet to the requirement of API Spec. 7.