I have the Detours High Tail UL. Love it. UL is for ultralight, and it's both light and delicate. Mine tore, I fixed it with duct tape.
I have carried up to the following at once:
Rain jacket, rain gloves, arm warmers, leg warmers, vest, a few Gus and a pop tart, small camera, flat-fix kit (tube, C02, levers, tiny multi-tool, patches), money, baggy of Heed.
I'm small, so my clothes are small too. You might want the bigger size one.
It wouldn't be enough for Credit Card touring if you needed rain clothes, for that I put a Tubus Fly rack on my road bike and used my front touring panniers.