1) The steel spine is used for carrying treads in the wood-steel staircases; 2) For the risers, there're 2 types for choosing: the height-adjustable twin tubular bar and the height-fixed mono tubular bar; 3) Welded steel spine and self-assembled spine for choosing; 4) Material: q235 common carbon steel; 5) Colors: black, milky white, flash silver; 6) Specifications: both standard and custom made available, pls contact us for details;