Described is a seat back comprising a curved rear wall bordered by a perimeter wall projecting forward from the rear wall. The curved rear wall and perimeter wall define a cavity in front of the rear wall and between opposing surfaces of the perimeter wall. The seat back comprises an upper part and a lower part. The lower part comprises a surface of the rear wall which is curved forward toward each side wall of the lower part and curved forward toward the base of the lower part. The width of the seat back tapers from a first width towards a second width at the base of the seat back.