The Ortlieb PS10 Drybags with Valve are lightweight, waterproof storage solutions for carrying compressible kit. They work in essentially the same way as a standard roll top drybag but with an air purge valve. You can keep rolling and compressing with the air valve open, then when all the air is pushed out of the bag quickly close the valve to maintain the maximum amount of compression. The air valve system makes these bags ideal for packing down down jackets and sleeping bags.
Please note the lengths listed above are the rolled down closed dimensions. For the open dimensions add 15cm to the length.