I have a 10+ yr old Carradice Nelson Longflap seat bag that fastens to the loops on my brooks saddle. I have a rack on the bike also, it keeps the seat bag from flopping around. I carry everything I need to take to work everyday. I carry clothes (not shoes), some food, tools and flat repair stuff, tubes. I've put much more than that in carradice, it can expand to become pretty huge. I've carried a round oatmeal container with my clothes and all sorts of odd items. It it doesn't fit inside, there are places outside to strap things to.