8 1/2" Steel Tricone Drill Bits 1-API or ISO 9001:2008 2-Delivery Date: In 7 days 3-Delivery ... ,134,136,137)These bits are designed to drill formations such as shales, medium soft limestone, ... ,214,215,217)These bits are designed to drill formations such as hard sandstone, dolomite, and ... 547G, 617G12 1/4311.1437G, 517G, 537G, 617G, 627G, 637G17 1/2444.5517G, 537G, 617G, 627G, 637G API 8 1/2" steel cone ...