Concentric String Tool
Description

Our concentric string tool is essential for helping you improve hole-opening efficiency. It centralizes the reamer even in irregular pilot holes, increases ROP, and allows you to use a range of pilot sizes. The tool is laterally stable and enables improved logging while drilling (LWD) response in the smaller pilot hole.

Features/Benefits

Force-Balanced Cutting Structure – Ensures tool stability even in demanding applications

Dedicated Nozzles – Optimized flow layout ensures efficient cutter cleaning and cooling

Premium PDC Cutters – Cutter type can be optimized to suit the demands of each specific application

Non-aggressive Gauge – Ensures the tool follows the pilot hole and does not deviate

BHA Design Flexibility – Can be used in tandem with underreamers for additional enlargement

Link:
http://www.nov.com/Segments/Wellbore_Technologies/Downhole/Borehole_Enlargement/Hole_Openers/Concentric_String_Tools/CS_Reamer/Concentric_String_Tool.aspx