Thickness and material are the two main factors that determine the hardness of a carton. There are usually three or five layers of cartons. Of course, there are still seven thicker layers. The more layers of cartons, the stronger they are. The three layers are not the flat plate with three layers, but two layers of flat plates with a layer of corrugated in the middle.

五层则为三层平板加双瓦楞;三层、五层纸箱又名单瓦楞和双瓦楞纸箱;纸箱材质也有多种，好的材质不光硬度高，而且分量轻，差一些的材质往往硬度很，很简易变形;市情上纸箱的材质从高到依序是“KK>KA>KB>AA>AB>BB", KK材质是目前对照好的材质。

Five layer is three-layer flat plate with double corrugated; three-layer and five-layer cartons are also listed as corrugated and double corrugated boxes; there are many kinds of carton materials, good materials not only have high hardness, but also light weight, and poor materials often have low hardness and easy deformation; in the market situation, the order of carton materials from high to low is "KK > Ka > KB > AA > AB > BB", and KK material is the current good material.

三层的厚度就充足承载一个正常成人年的分量，表面平滑有质感，KK好是好，可是售价也是对照贵的，AA，BB材质虽硬度稍弱，可是搭配五层的厚度，也有很高的硬度，足以保护好产物不受破损。

The thickness of three layers is enough to carry the weight of a normal adult year. The surface is smooth and has texture. KK is good, but the price is also relatively expensive. Although the hardness of AA and BB materials is slightly weak, but the thickness of five layers also has high hardness, which is enough to protect the products from damage.

我提议卖家根据自身的需求，选择差异类别的纸箱，譬如易碎、珍贵物品不妨运用五层AA纸箱，寻常经摔的物品，或许商品自身自带纸盒的，选择三层的就充足了。

I suggest that sellers should choose different types of cartons according to their own needs. For example, fragile and precious items, they may as well use five layers of AA cartons. For ordinary items that have been dropped, or if the goods have their own cartons, they should choose three layers.