Ivy League(tm) provides a complete collection of classic classroom furniture. Its timeless style meets specific classroom needs now and adapts to the needs of the future. It has unbeatable quality, incredible durability and an industry-leading 15-year warranty.Ivy League Series 10 classroom chairs have seats and backs that are thermoset hard plastic in four fixed sizes or with adjustable legs. Frames are made of 18-gauge steel. Optional bookrack available with 18″ chair only. The X-brace model is stackable.