HMG Roll-Top Stuff Sacks - are Dyneema stuff sacks with roll-top closure and round-bottom which provide an extra barrier of protection inside your pack.

If keeping your essential gear dry is a priority, these Roll-Top Stuff Sacks are a must-have for any packing system. Available in 6 different sizes, they can accommodate everything from a small food bag to a pack liner.
They are perfect for storing your personal items, toiletries, down jacket, quilt, it can work as a clothes bag, overnight food bag or as a liner/dry bag.
an expedition style sleeping bag, as a liner/dry bag for a 15-30 Liter pack or will keep your backpacking, mountaineering or packrafting gear perfectly dry inside your pack.

While not a completely sealed dry bag, they come very close when rolled down sufficiently, providing maximum water resistance without the extra weight.