... and stainless steel9.Advantages:1) Shape luxury, showing the lordliness.2) The line of frame is distinct and very strong sense ... imitation wood grain , fireproofing ,dampproof ,it is elegant as the wood window but more durabler than it .6) Unique pulley ... ,make the window sliding smoothly,convenience,no noise.7) Guard against theft , security. some corners of the window: factory of aluminium ...