Establishments primarily engaged in manufacturing innerspring mattresses, box spring mattresses, and non-innerspring mattresses containing felt, foam rubber, urethane, hair, or any other filling material; and assembled wire springs (fabric, coil, or box) for use on beds, couches, and cots. This industry also includes establishments primarily engaged in manufacturing dual-purpose sleep furniture, such as convertible sofas and chair beds, regardless of the material used in the frame. Establishments primarily engaged in manufacturing automobile seats and backs are classified in Industry 2531; those manufacturing individual wire springs are classified in Industry 3495; and those manufacturing paddings and upholstery filling are classified in Industry 2299.