8 1/2" Steel Tricone Drill Bits 1-API or ISO 9001:2008 2-Delivery Date: In 7 days 3-Delivery ... , with high durability and maximum penetration rates. 2,Soft to medium formations(121,124,126,134,136 ... days SizeBit TypeIn.mm6152.4517G, 537G, 617G, 637G6 1/2165.1517G, 537G7 7/8200.0517G, 527G, 547G, ... 617G12 1/4311.1437G, 517G, 537G, 617G, 627G, 637G17 1/2444.5517G, 537G, 617G, 627G, 637G API 8 1/2" steel ...