20L - Love it
Whether I am flyfishing, going on a day hike, backpacking, canoeing, or snowshoeing, I pack everything I need dry in this. I believe it works better than a pack cover in most circumstances, especially flyfishing because I can't find a pack cover that would do a better job than this bag. I simply stuff anything I need to keep dry inside. For backpacking I can fit all my cloths and sleeping bag inside, and not have to worry about them getting wet if it starts raining, or I happen to fall into the river.
It is also very durable and well stitched and seamed. I would highly recommend this. It has lasted several years with no signs of wear and tear.