Just for clarity and for when you search for some on the internet; in the US we call them "Stuff Sacks"

All good advice up above. I need my gear organized so use a combination of stuff sacks, Ortilieb packing cubes, zip locks and nothing at all.

Have fun playing around to figure out what works for you! -it's an evolving process. Kind of like putting a puzzle together but the puzzle always changes based on what is needed for each trip!!