I use these. I keep one one or two rolled up in the camelback in case I need to protect the camera or other gear. Right around $12.- @ your local W-mart for a pack of 3 bags ( sm., md., lg.). After about 3 years of use and being caught in some killer downpours, everything has stayed dry. It is sort of a sil-tarp type of material, very light, yet water proof.