This super lightweight 15D nylon stuff sack is coated with silicone on the outside & PU on the inside with fully taped seams & a roll top closure. It is completely waterproof & dustproof to protect the contents from...water & dust! The fabric is translucent making to easier to identify the contents. Make sure that you fold the top over at least three times when closing the bag to ensure a watertight seal. I have become a bit of an addict of Exped stuff sacks, using them to organise & protect my kit whenever Im out & about, or even just in my everyday work bag.