This 9" solid wood on wood foundation provides a solid feel that will help the set hold its firmness, provide a stable system, and extends the life of your mattress. You will not see any bowing due to solid 2" x 3" wood runs which are the entire length of the foundation, from head to toe. You will get 40% more cross strength with 1" x 3" wood cross slats from this foundation and seat edge strength as well.