"Upholstered seats" are those having a soft layer of, for example, wadding, tow, animal hair, cellular plastics or rubber, shaped (whether or not fixed) to the seat and covered with a material such as woven fabric, leather or sheeting of plastics. Also classified as upholstered seats are seats the upholstering materials of which are not covered or have only a white fabric cover which is itself intended to be covered (known as upholstered seats " in muslin"), seats which are presented with detachable seat or back cushions and which could not be used without such cushions, and seats with helical springs (for upholstery). On the other hand, the presence of horizontally-acting tension springs, designed to attach to the frame a steel wire lattice, taut woven fabric, etc., is not sufficient to cause the seats to be classified as upholstered. Similarly, seats covered directly with materials such as woven fabric, leather, sheeting of plastics, without the interposition of upholstering materials or springs, and seats to which a single woven fabric backed with a thin layer of cellular plastics has been applied, are not regarded as upholstered seats