back:hight density and soft P.U,high active inflaming element,coldly firmly becomes spongy a body forming. base :high dendity and soft P.U,sopring erectionof steek work,coldly firmly becomes spongy a body forming. shell:the multi-elements compound material quality projectsthe forming.the anti-impact.provides for old age,guards against discoloration. coat :after anti-corrosive treatment.electrostatic powder spraying railling :high density ultra soft PU projects the forming . written board:high strength casts turns over thebearing,the board is high densityboard,outside covers the melamine surface.