... , RQ, NQ, HQ, and PQ. T2 Series Double Tube Core Barrels: The T2 Series are thin wall double tube core barrel, used for surface ... . Available in diameters 46, 56, 66, 76, 86, 101mm. T6 Series Double Tube Core Barrels:These are a continuation of the T2 ... extra hard rock formations. Available size 48 and 60mm. WF Series Double Tube Core Barrels:They are geotechnical core barrels primarily designed ...