Why are the fabric specifications used for the backpack's body, bottom, and front pocket different from each other?

The force and friction applied to each part that makes contact when putting down the backpack or packing gear are different. Hegiorsak's Ultra Cube 55 backpack distributes three fabric specifications according to the use of each part^[1].

The part that makes the roughest contact is the bottom. For the bottom surface, which frequently rubs against rocks or dirt and experiences friction, ULTRA400X (Ultra 400X) with reinforced durability was applied^[2]. Generally, the larger the indicated number, the thicker the yarn becomes, making it stronger against friction and tearing, but the weight also increases proportionally. Since wrapping the entire backpack in thick fabric would make it heavy, relatively lighter ULTRA200X (Ultra 200X) was used for the main body surrounding the load to reduce the weight burden^[3].

The front storage space is a place where items are frequently put in and taken out. For the front pocket, ULTRAGRID (Ultra Grid) fabric was applied, which stably holds its shape even when items are stored inside^[4]. A fabric with grid-pattern reinforcement yarn added to the outer surface helps reduce the phenomenon of the pocket sagging or drooping downward due to the weight of belongings. It is a configuration in which the fabric thickness and weave were appropriately selected according to the friction and load experienced by each part.