Stylish, black Stack Chairs are made of polypropylene for superior durability and lumbar support. Chairs feature solid, chrome frames and sculpted backs with an integrated opening for enhanced mobility and stacking. Stack up to 16 chairs on Boss D100 Dolly (not included) or five on the floor to save storage space. Boss Ganging Clamps (not included) are available to attach multiple units together at the bottom of the leg.