7/16" steel rod and 5/8" steel tubing supports perforated polypropylene seat and back. Upholstered option of foam padded seat and back molded plywood interior. 5296, 5296U, 5297, and 5297U utilize 5/8" steel tubing only. Stacking styles stack 15 freestanding and upholstered 25 on the #94 dolly.