I manage to get two 700x25c tubes, two CO2 cartridges, a multitool and tire levers into this little guy. Tight, but doable. It also requires less rail space for mounting, which is important since my seat is further forward than most. This prevents me from using the common clamp-style mount seen in topeak and other brands.One things I wish for is another inch of strap, since a full bag leaves less than an inch of velcro to secure the bag once it's wrapped around and cinched down. If I don't cinche it down tight, the strap can come undone when going over bumps... followed by a thump against my back wheel to alert me that my seatbag is parting ways with me rapidly.Overall a great bag which works well and looks great.