Air prunes roots to encourage branching. Dividing walls and channels inside the cell direct the roots downward. As the roots grow into the open-bottomed wells, the leading end dies back and the root sends out side-shoots creating a dense outward-branching root mass. Since roots don’t hit container walls then spiral around, seedlings are stocky and more robust and grow faster as transplants. 90 pots, 3x3x4"; 18 pots fit neatly in a standard 10x20" tray. Mesh bottom tray not included.