The Traditional sled base chair features the Royal one-piece, injection molded polypropylene shell. The seat is reinforced with ribs that allow greater upper back flexibility while still supporting the lower back, mounted on a 3/4", 16-gauge steel sled base frame. This versatile seating solution makes sliding chairs easy for any classroom configuration. Available in chrome or black powdercoat frame with felt glides. Optional field installed book basket fits 20"A+, 18"A+, and 18" sizes.