It is a cardboard made and used in many specialized filling and packaging fields,
- The duplex cardboard classified as follows :
-GD Grade: cardboard, made of recycled materials, consists of three layers 
The upper layer : a white layer covered with a layer of packaging to facilitate printing process and colors adhesion with cardboard
The middle layer( interior filling) and it is  a gray layer.
The lower layer : it is also gray but it does not contain packaging layer.
-GT Grade: it is similar to the previous classification with the used material of made and cardboard formation, but they differ in one thing which is the lower layer is  with white color.
-GC Grade : cartoon made of raw materials so it is the best choice in packaging foods and medicine. It is divided into two types ,  according to the cardboard layer division :
First : the upper layer, a white layer covered with a layer of packaging to facilitate printing process and colors adhesion with cardboard, the middle layer( interior filling) is ivory and the lower layer is also ivory or white but it does not contain packaging layer.
Second: the upper layer is white covered with a layer of packaging to facilitate printing process and colors adhesion with cardboard, the middle layer( interior filling) is  white layer and the lower layer is also white but it does not contain packaging layer, and this type of cardboard called ( Ivory board).
 

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