The seat (tip-up version) and the backrest are made of lexible ire retardant cold-foamed polyurethane. The polyurethane, after having been moulded together with the external upholstery fabric to create one block, is directly injected on the internal steel frame of seat and back. Seat can be tip-up type by counterweight mechanism, or of ixed type. Only in the version with ixed seat, the internal seat construction is with a plywood panel and seat upholstery could be eventually removable.