Furniture Design Bam Klein Sofa by Xie Fengcou Bam Klein is a sofa inspired by the topological form of the Klein bottle. The seat, backrest and armrests are shaped as one continuous curved surface, so the usual distinction between inside and outside is removed. The internal frame combines engineered wood and reinforced steel, while high resilience foam cushions and fabric upholstery provide ergonomic support. Slender black powder coated steel legs give the sofa a light appearance and keep the structure stable. The single piece construction reduces joint stress and improves durability.