... Material: Alloy steel Certificated by API&ISO9001:2008 8 1/2" New PDC Bits for Well Drilling Description about sell rock ... on .Specification: diameter from 5-1/8” to 13-1/2”.There are different PDC (polycrystalline diamond compact) grades and shapes ... :1. Andesite, marble, metamorphic schist (For hard, low abrasive formations)2. Gneiss, Diorite, Basalt (For hard and abrasive formations)3. Quartz ...