Here is a copy of something I posted on another thread regarding the
Green Guru Hauler Bike Pack:
I use one of these on my bike and really like it a lot. It has a stiff plastic insert on the bottom, so it's like a removable rack. It's expandable so it's only as long as it needs to be depending on how much stuff you have in it. It comes with a shoulder strap, so when you reach your destination it can be worn as you would a messenger bag. When I don't need to carry lots of stuff, like when I go out for lunch, I can easily remove it from my bike so I'm left with a bike that has no added weight from an attached rack. It's very durable and waterproof and I like that it's made entirely from recycled materials. Only downside is the straps that go through the saddle rails are short, so it takes some practice inserting them, but that's a minor complaint. Also, it only has one outside "pouch" that is a decent size 2-dimensionally, but not 3 dimensionally, if you know what I mean (It's a flat pouch. I would have designed it to have more depth). I fit my smartphone and keys in it, and could probably stuff my wallet in it, but not much else. Not a huge problem - it's quick and easy to undo the side clasps and open the main bag while it's attached to the bike.