2 x Vitra AC3 Antonio Citterio Chair with chrome and black textile.2 x Vitra AC3 Antonio Citterio Chair with chrome and black textile. The AC3 is one of Vitra's perfectly designed cantilever chairs. It is classically elegant and ergonomically very comfortable. It is used both in the office and in the upscale living area. In addition to its timeless design, the AC3 is characterized by a very high manufacturing quality and durability. Structure: bent tubular steel frame with cantilever principle, bent armrest