I am looking for a compression sack to contain my JRB Nest, and my Rev X 30 degree. Ideally they will take up the normal spot for a sleeping back in my Osprey Kestrel pack. I really have no idea what literage I should choose but I have been looking at the 6L version of this:

http://www.rei.com/product/730882/se...ssion-dry-sack

Any thoughts? The JRB came with a sack and the Rev X did not. Thanks!