1.Gas Spring,Lift,Cylinder,Strut for Chair,Table 2.Black ,chrome Surface 3.SGS BIFMA 4.ISO9001 Certificate 5. ... , two year warranty(Normal)Class 2---1.5mm, cheaper price, three year warranty(Better)Class 3---2.0mm, expensive price, five year warranty ... (Much Better)Class 4---2.5mm, more expensive price, five ...