1.underground drilling steels 2.High quality, cheap 3.good after-sales service 4.wide size code 5.API&ISO API&ISO underground drilling steels bits with many IADC codes 1. Introduction about us:We are Hejian Deris Petroleum Drilling Equipment Co., Ltd Drilling Supplies Marketing Dept. specializes in drill bits, drill pipe, Mud pump and stablizers for water well, oil field, construction, geothermal ...