Exped Waterproof Rucksack Liner Corn Yellow S (50L)
The sack in the pack. Large, pack size versions of the Fold-Drybags. In contrast to packsacks with round bottoms, waterproof Pack Liners are better shaped to perfectly fit a backpack and completely fill the space. Comes with a fast access roll-n-fold closure. Bright inner PU coating lights up the interior of the bags for better visibility.
This item is the medium sized one in the image.