The openings on the inside tube rotate around so that it opens first at the bottom and then in gradual steps to the top.

This assures a fair proportion of grain samples from the bottom levels as well as from the top. The Spiral Probe is highly recommended for sampling grains when foreign material is apt to be heaviest near the bottom of a truck. The construction of the probe is a double-tube brass with a 1⅜" outside diameter and heavy bronze point.