There are 3 layers in cartons (inner flat layer- corrugated layer- outer flat layer) or 5 layers (3 layer carton - corrugated layer – flat layer). The inner flute is mostly made of recycled material. 5 Layers carton is used for heavy products as household appliances .
The carton boxes ends can be glued together or fixed with metallic pins.
Flute types: E flue, B flute, C flute, .. .