Instead of 2" x 12" stringers, this new lightweight constructed stairs are made of a 2"' x 4" running the entire length of the stairs on the side. While the stair treads and risers are made up of 3/4" OSB. The triangles and the edges are capped with lightweight steel held by glue and nails. It has been reported in a main staircase (1st to 2nd floor) the underside would be covered with drywall for added protection, but when used in an unfinished basement, the stairs would be left as seen.