"Songmics fashion style office chairs with adjustable seat height; bilateral arc wing back, waist size according to body curve design, protect and reduce pressure of spine; bilateral handrail according to ergonomic design of the bow, if you put your arms on, you will get a complete relaxation. And it have the resting mode which you can shake back and forth slightly. Easy installation, equipped with installation tools. - The material is now upgraded and with quality assurance, like armrests, tray, and wheels, they all provide by the best manufacturers among the similar products. - All parts of PU are used the same surface PU like its seat which will effectively reduce the chemical odor.- Thick and high-density foam has comfortable sitting, and without deformation in prolong using. - The accessory screws box are plastic packaging and with numbers to prevent its loose or missing. - The use of anti-loose screws, which can effectively prevent the screw loose after a long time using.- All models are added with a screw as spare screws which ensure its using security. Note: - Please put the side ""FRONT""on the tray forward when installed. - Lift the lever under the seat to raise the seat; lift the lever and sit on the chair to lower the seat. Pull the lever outward to release the tilt mechanism; push the lever in to lock the mechanism - In resting mode, the seat and backrest will move together when you lean back and the inclination of backrest can not be changed independantly. Product Parameters: - Material: PU, Organic Polymer Foam, nylon - Color: Black - Base diameter: about 70 cm,tota Height: 112-122 cm,Back height: 76 cm,Seat Size: 54 x 51 cm (Width x Depth),Seat height: about 45-55 cm - Max.load: 150 kg  Shipping List: - 1 x Office Chair - 1 x User Manual(ES, DE, EN, FR, IT) - 1 x Installation Tool."