8 1/2" Steel Tricone Drill Bits 1-API or ISO 9001:2008 2-Delivery Date: In 7 days 3 ... , with high durability and maximum penetration rates. 2,Soft to medium formations(121,124,126,134, ... and broken formations with hard cherty streaks Model6-26( inch) TypeTricone bits, Steel tooth bits, PDC bits ... , 617G12 1/4311.1437G, 517G, 537G, 617G, 627G, 637G17 1/2444.5517G, 537G, 617G, 627G, 637G API 8 1/2" steel ...