The back is mesh, allowing for a cool climb even under high loads. I used it twice for day hikes. (Mount Kintoki, Mount Oyama) In my subjective opinion, it's still in beautiful condition. Also, as a bonus, I will include a mess tin (for cooking 1 cup of rice), chopsticks (split type), a spoon (folding), and an aluminum wind shield. Lowe alpine AirZone Active 18 Product number: FTF-19 Color: Black Size: 52 x 27 x 21cm Weight: 0.77kg Capacity: 18L Back length: 46cm ・AirZoneLT™ system ・With rain cover First come, first served, you can buy it immediately. I will ship it as soon as possible. Size...11-25 L