The BoB dry sack is actually pretty darn waterproof as long as you roll it over and close it correctly like a dry bag. We rode through two straight weeks of rain in the Pacific North West without much, if any, water leaking in. I agree with sunset though, if something must stay dry, pack it in another dry bag like a seal line bag or some other lightweight dry sack. For tents, cooking stuff, stove, bike stuff etc. a little damp won't really make much of a difference. We had a bigger problem with things getting wet by packing wet gear in the bag and it soaking things around it. It happens! One other cool thing about the BoB. It might not look very pleasing to the eye, but a normal sized Rubbermaid tote fits extremely well in the trailer bed. I haven't used one for touring, but I have considered it.