The compression point is the first part to go through the ground and is attached to the Master shaft or quick shaft. It breaks rocks, splits roots and other debris as it makes its way under the pavement and opens a hole larger than the shafts. This particular point is the smallest point that we sell. It is actually 1-3/4" in diameter and will make a hole large enough to accommodate a 1" Sch 40 pipe with a coupling.