It is suitable for overburden with complex geological conditions, 
such as pebble, fissure, dry stone, Boulder, construction backfill
 waste, etc. It can be drilled at any angle with high straightness.
Its Advantages as follow,
Straightness：The straightness of the hole can be ensured under different geological structures.
Adaptability：In complex geological structures, such as pebbles and construction waste, the efficiency of drilling can be guaranteed.
Lower torque：Compared with the eccentric drilling system, the torque is smaller.
Easy to unlock and relock: Easy to relock after unlocking.
Drilling at any angle:Concentric drilling tools can be drilled in vertical, horizontal and inclined conditions.
Environmental：Compared with eccentric drilling tool, it is more suitable for urban construction because of its smooth drilling, small vibration and low noise.
Application：Concentric drilling tools are mainly used in pile foundation and anchoring engineering.