There is a gap between the backpack and the back for good ventilation and comfort. This backpack is growing in population of backpacks, for those who have trouble with sweat on their back that tend to trap heat
Easy to install by simply attaching it to the belt of your backpack. The space between the back allows the wind to pass through, making it cool and comfortable to use
It also prevents your backpack from getting wet from sweat on your back, so it is very clean. When not in use, it is compact enough to fit into a backpack drink holder
The filling is made of polyethylene resin with high cushioning, so it has a good cushion, fit, and is breathable and has little tightness. The cover is made of breathable mesh
Product Size: Diameter 3.1 inches (8 cm), Length 4.7 inches (12 cm), Product Weight: 2.8 oz (80 g), Material: Main body: Polyester, Filling: Polyethylene