"Fits the bottom of my Granite Gear pack perfectly"
I purchased the largest of these pack stuffers for use in my Vapor Trail. It perfectly fills the bottom of the pack and is made of the same cordura and silnylon that the pack uses, matching it for sweet style points. It feels almost overbuilt in terms of quality. Be careful filling it. If you really overstuff it full of something like a big poofy sleeping bag, it's pretty tough to get it into the pack because you have to shove it in skinny-side-first and rotate it to fit into the bottom of the pack. Kind of a pain, but as a plus Granite Gear has a little pull loop on the corner of the stuffer that makes removing it super easy.
I ordered the 18, 13, & 12 L bags. They work great in a backpack to keep your items organized. I used these in Afghanistan and they were very durable and kept my clothes and other items clean. I have also used them in a carry on rolling bag for organizers and they work great that way too!