Check the listing for details. Modern Stacking Chairs Set of 4 in Black with Ergonomic Design, Polypropylene. Color: Black, Condition: New. Listed at 266.57 USD. The back shell and seat plate are injection molded using brand-new polypropylene and fiberglass. The seat and backrest are divided into two parts. The backrest features a sleek curved design that conforms to the contours of the human back, providing a comfortable support experience and adhering to ergonomic principles. Tripod: Made of high-quality 11mm solid steel, with an arch-shaped structure, the surface is treated with acid pickling, electroplating, or electrostatic spraying. It boasts high overall stability and can support a load of 180KG According to the general office chair test, it can bear a weight of 180KG, with a one-time tensile test of 108kg for the backrest, holding pressure for one minute, and a rubber back of 40KG for 120000 cycl.