Plastic/Polypropylene/Metal Provide all-day comfort with this set of 5 sled base stack chairs with air-vent backs. These chairs are contoured with an ergonomic design for optimal comfort and back support. Polypropylene seat and back with powder coated frame finish 5 Plastic stacking chairs: Steel frames can support up to 881 lbs. Sled base with plastic floor glides for added stability PRODUCT MEASUREMENTS: Overall Size (5): 18"W x 21"D x 33"H; Seat Size: 17"W x 18"D x 17.5"H; Back Size: 17.5"W x 15"H; No Assembly Required