4: The back seat connection (Corner) seat and back is split, the use of steel or steel connection plates, usually 6mm or 8mm thick. But less than 6cm width steel plate, must 8mm thick. 5: The gas bar called the stretch down the lever for adjusting the height and rotation of the chair. 6: Chassis hold the seat part, the following is connected with the gas bar. 7: back steel frame, plastic frame of the chair, using a combination of mesh is made with breathable.