People's Republic of China (PRC) national standard "CAD engineering drawing rules" stipulates that A3 size is 297mm times 420mm. Picture frames come in two formats: one with edges and the other without edges. No binding edge, same as A3 size, with binding edge, and space is reserved on the basis of A3 size. The binding edge is 25mm, the reverse side is 10mm, and the upper and lower sides are 10mm.