Poor flatness and uneven thickness of tempered glass will cause optical distortion. When it is used in laminated glass, the uneven thickness will result in optical deformation, deteriorating further the visual effect of the product. The local thinning of the laminated glass can also affect the bonding of the glass panes. If tempered glass with poor curvature is used in insulated glass, it will cause uneven sealing. It will adversely affect not only the quality of product appearance but also the sealing quality. In addition, it may cause excessive partial thickness which makes the installation more difficult.