Grazie's Perfect Pivot™ is a patented frictionless mechanism that exactly mirrors natural body movement to provide the ultimate in sitting comfort. This mechanism allows the backrest to move 15 degrees about an axis of rotation that is through the hips of the sitter. Injection-molded polypropylene shells and seat liner board. 12-gauge steel underseat structure. Optional upholstery over 1" thick seat foam and ½" thick back foam.