The RootBuilder II container system has many holes with downward facing protrusions all around the container. This design allows roots reaching towards the container wall to locate the air holes immediately.

The downward protrusions make it virtually impossible for the directed roots to escape root tip pruning. Another feature of the angled protrusions on the containers is that they not only force roots downward to the air hole for proper air pruning, but they also create shade, keeping your entire plant's root system much cooler.