Ah, I just eye balled it and my bag looked bigger.
I bought the medium as I needed to hold tent and my sleeping pad in one bag - the medium fit the bill. It was originally bought for the Griso at last years National Rally and it was to go across the bike - I also wanted to limit just how wide it could go and some what limit how much mass would be put in it. Over loaded it could affect handling in a bad way.
I got black, mainly because I got the Giant Loop in yellow, and after getting it, think black would have been a better choice. My motivation for the color.
It works so well I've been tempted to get a second one and hang them off like bags (on the Griso anyway).
Anyway, for long weekends when I hotel it, tanks bag and the duffle are plenty. Tenting, then the duffle gets the big stuff and I use saddlebags for the usual stuff and my sleeping bag. Still, a second bag is not a bad idea.