Adavantage
1. the concentric design is more reliable and less torque than the eccentric.
2. large impact power to make high speed drilling.
3. straighter hole.
4. easy to follow the casing.
5. reverse rotation and withdraw the pilot bit to use it for next holes.
| A | B | C | D | E | F |
| Outer Dia. of Casing Tube | Inner Dia. of Casing Tube | Reamed Dia. | Min. Inner Dia. of Casing Shoe | Hammer Type | Drill Pipes |
| mm | mm | mm | mm | mm | |
| 114 | 101-103 | 125 | 93 | TDS79 | 60 |
| 140 | 124-127 | 152 | 113 | TDS98 | 76 |
| 146 | 127-132 | 154 | 115 | TDS98 | 76 |
| 168 | 149-155 | 184 | 138 | TDS122 | 76,89 |
| 178 | 159-165 | 194 | 148 | TDS122 | 76,89 |
| 193 | 173-180 | 206 | 164 | TDS139 | 114 |
| 219 | 199-206 | 234 | 185 | TDS139,TDS180 | 114 |
| 244 | 224-231 | 273 | 219 | TDS180 | 114 |
Order Guide: A+B+C+D+G