... specializing in the design and manufacture of premium diamond drilling tools for the world engineering: geotechnical exploration, Mining exploration, Oil ... , φ160, φ170, φ219, φ27514. Chinese Standard Metric Core Bits for Double Tube Core Barrels: φ56, φ59, φ75, φ9115. Chinese ... Standard Metric Core Bits for Wireline Core Barrels: φ59, φ75, φ91We can manufacture all kinds ...