The Pilot reaming shell is the benchmark for knowledgeable drillers where quality and reliability are valued above initial cost. The importance of the reaming shell in maintaining hole direction and gauge cannot be underestimated. At every bit change, the new bit is expected to reach the bottom of the hole without interference. As the shell typically lasts the life of several bits, the selection of the best available reaming shell is an investment in productivity and overall cost of the project.
If longer than standard shells are used to minimize hole deviation, a corresponding inner tube extension must be used.