it looks like a thin nylon (im not that savvy so just a guess.) weights about 2oz has full velcro top with buckles. i turned it inside out and filled it with water...some slight dripping from the seams (not really the seams because they are taped, coming from where the tape ends.) might be able to seam seal for better results. so not submersable, but would work in the rain i am guessing.
for 3.55 shipped, it is water proof enough for me. obviously, if your life depended on it, i would pay a bit more and get a real one, but for a recreational hiker/camper, they met my expectations at first glance/test.