I bought this as a spare but never used it. Lightest weight at only 30g Capacity 9L How about using it as a sub-backpack? Brand: Black Diamond Product Name: Silo 9 Product Description: This is one of the lightest packs on the market, weighing only 30 grams and folding up to the size of an egg. It's perfect for travel when you don't want to increase the amount or weight of your luggage, and it's easy to pack whether you plan to use it or not. Price: ¥5,500 (tax included) Weight: 30g Capacity: 9L